A Hot, Wet Sister and Her Regretful Brother

Story by Joshiah on SoFurry

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#15 of Incest Stories (Others)

Not the best title, but perhaps one of the best stories I've ever done, this is a superbly naughty commission for FA: Lightweaver!

In this story, a Clydesdale by the name of Mark is living it up in his first year of college. He has his own flat outside the city, a job that keeps him just busy enough to stay out of trouble, and all of the right friends to party with on the weekends.

He also has a younger sister, just past the age of 18, who has come to visit him for a weekend, so she can see what the university life is like. Mark has always viewed her as young, immature little mare, but when she forgets to bring her heat-inhibiting pills...that perspective is lost forever in a myriad of sexual acts.

Please don't use either of the characters within without FA: Lightweaver's permission.

As always, read, comment and enjoy!


Getting away from home and living on your own for college was a beautiful thing, at least, for the most part.

Anyone who had ever gone to a university and stayed in a dorm could tell you about the awesome parties that just seemed to pop up out of thin air, the shenanigans that you would get into whether you liked it or not, and the fact that your sex life was suddenly about to get a lot more private, thanks in part to the massive lack of privacy that most dorms had.

Of course, if you wanted that kind of experience, but wanted to have the privacy to have a better sex life, you could be like the lucky kids who saved up their money in high school, and had the funds left over to get a place that was just slightly off campus, allowing for easy access to parties and other sorts of debauchery, while still having all of the privacy you could want in your own home, without having to deal with roommates and drunken idiots on a nightly basis.

For Mark, having his own flat just steps from the campus border was the perfect balance of party life and privacy, and even a few weeks into his first semester at the university, he was still stoked about just how wonderful his life was turning out. The promise of everything that college was going to offer was actually coming true for him, and without his parents around to judge his every move, he'd truly never been happier.

"...You know, I just really don't feel like going to class today," Mark groaned to himself, as he barely found that he had the strength, or at least, the determination to get out of bed. He could easily lay there and stay at the ceiling all day, knowing that he hadn't missed a single class since the semester started, and there were no exams that afternoon. He wasn't nursing a hangover or anything of the sort, but as amazing as college life was, he was truly starting to experience the exhaustion that so many first year students experienced: taking too many classes, going to too many parties, and eating too much junk food too often created a world in which freshmen were quick to try and find a way to balance out their poor choices.

In the case of Mark, it was in the form of finally breaking down and deciding to sleep in, instead of going to a lecture hall and sleeping in a chair, sitting upright.

A typical Clydesdale from a relatively normal family, Mark was a little bit on the tall side, and his body was filled out, with the trademark muscles that every breed of horse carried proudly in their thick, rippling legs, but otherwise, there wasn't a lot to make him stand out in a crowd. He was certainly an attractive male, and he'd be lying if he told anyone he was still a virgin, but he was aware enough of his own looks to be a little picky with who he took to bed, even in the early days of college when everyone seemed to be encouraged to experiment.

...I guess I am living on my own. No reason I can't do a some experimenting right now, actually, Mark thought, as he finally rolled over and put his hooves on the floor. He stretched upright and wiggled his back around a little bit, before he actually stood up and reached for the sky. He shook the platinum blond locks of his mane out of his view and looked down, deciding that he wouldn't even bother with his pajama pants if he was going to spend the morning in front of a computer screen with his length in his paws...and it looked as though his body was already on board with the idea, as his massive cock began to put a strain on the loose fabric of his sleepwear.

Knock knock knock

"You have got to be shitting me. I swear, I get my own place, and every time I decide to do this, someone comes over and messes it up for me!"

Doing his best to tuck his member into his thighs, Mark made his way through the mess that was his bedroom and scooted through the living room of his flat, right to the front door, where he head another quick, impatient series of knocks. "I'm comin', I'm comin'!" he yelled out, wishing that he was crying those words with a much different meaning, but alas, those hopes were already fading from his mind. Frustration was the biggest killer of his sexual moods, and he was brimming over with it when he finally opened the door to his place...and saw a very familiar face.

"Tam? Wh...what are you doing here?"

"What? Your little sister can't come and pay her brother a visit at the university?" Tam asked, as she walked right past her older brother and into the landing of the flat. Mark was still so caught off guard that he didn't react until she was well past him, and he shook the cobwebs from his mind before closing the door behind her. "Of course, this isn't really the university. Mom and Dad didn't tell me that you were actually living a few blocks away when they gave me your address."

"I wasn't exactly expecting company," Mark admitted, glad that his sister hadn't noticed the predicament between his legs, or at least, if she had, she was keeping quiet about it. "And why didn't Mom and Dad call me to let me know you were coming?"

"Looks to me like you just woke up, Mark...and I'm not sure, really! I figured that they would have called you a little while ago, at least."

Mark put the bridge of his muzzle in his paw and winced his eyes shut in even greater frustration as he realized who must have been calling while he was trying to sleep that morning. No doubt, it had been his parents, and at least then, he would have had an inkling about Tam getting there. Instead, the slightly shorter, much bustier and far more playful mare arrived unannounced, and Mark didn't even have a chance to clean up the mess that was his flat.

"This is an awfully nice place you've got, Mark. You really saved up enough back in high school to pay for all of this?"

"It wasn't easy," Mark confessed, "But I like to think it was worth it...and you still haven't told me why you're here. You always have an ulterior motive."

Tam rolled her eyes and crossed her arms as she glanced back over her shoulder at her brother. Her tail gave a quick flicker of annoyance as she set down her purse, and shrugged a backpack from her shoulders. "Maybe I really am just in town for a visit, Mark. I know you've always treated me like a kid, but I'm going to be picking a university next year, and I thought I could trust you to put me up for a couple days while I looked around and got a feel for this one."

Just barely past the age of 18, Tam was likely to graduate from high school early and start college as quickly as she could, and her relationship with her brother was just as she'd described: he viewed her as being immature and bubbly, without the kind of hard-nosed determination that one would need to press on through college courses.

Of course, she was already there, and Mark couldn't fathom putting his sister out on the street. "That's...that's actually very responsible of you, Tam. I'm proud of you for doing that."

Tam's eyes of sparkling jade lit up with an even greater shimmer at the compliment. She was trying to look the part of maturity, as well, wearing a thin jacket over a button up t-shirt, and a long, flowing skirt of black draped down from her waist and settled respectfully at her knees. She could easily have passed for a university student, given her beautiful mane, the allure of her eyes that twinkled with a greater intelligence, and the fact that her body was plenty filled out, even for a mare. "You really think so, Mark? It's about time you came around and realized what a smart cookie your sister was!"

By contrast, Mark looked like a wreck, and much more like the sibling that would still be in high school, not taking life seriously enough. "If you're willing to put in the effort, then you're doing something right, Tam. You can stay as long as you need to."

"Ooooh, thank you so much, Mark!" Tam cheered as she fully turned around and jumped forth to wrap her arms around her brother. Just by reaction, he embraced her in turn, completely forgetting about the fact that his member was still slightly engorged, and now, bumping against his sister's knee.

This isn't happening. Think about nasty things. Spiders. Old spiders. Old spider nuns with bad teeth. S...stop it, dick! Go down!

Mark's battle with his own mind seemed to be a lost cause, and he was sure that Tam would freak out, but instead, she just giggled when she looked up and saw the concern on his face. "Relax, Mark...I can tell you just woke up. It's my fault for not letting you take care of your... problem, first."

"We are not having this conversation, Tam."

"Suit yourself," she said, allowing the subject to be dismissed. Mark didn't want to think about why Tam was suddenly so comfortable with sexuality, especially that of her own brother, but she released him with a quick, family-friendly peck on the cheek and sauntered into his kitchen, unloading her purse into the medicine cabinet. "Don't have any classes today, do you?"

Mark scratched the back of his head nervously. "W-well, I...I mean, I did, but I decided that I was just gonna rest up for a day. No exams or anything."

"No judgment here. It's smart to take a break sometimes, I'm sure," Tam replied, showing she agreed with the idea. "You just go about your day, Mark. Don't let me interrupt. I'm sure you won't even notice I'm here."

"I've got a guest bedroom to make sure that I don't notice you're here," Mark teased, sticking out the tip of his tongue a little bit, and receiving a middle finger in immediate reply. "And watch the filthy gestures, or I'll tell Mom."

Tam rolled her eyes yet again and picked up her things, walking down the hall towards the bedrooms. "I'm sooooo scared, Mark. Left door, or right?"

"Left. Feel free to make yourself at home."

**

The first day with Tam on campus was rather uneventful for Mark, to the point that he almost didn't notice her being around. He occasionally had to fend off the males (and even some females) that were eyeballing her, but for the most part, she just tagged along with him and sat in on a couple of his classes, getting a feel for the way that campus life worked. She was envious of him for having his own flat a few blocks away and closer into the city, knowing that she wouldn't be able to save up enough money to pull off such a thing, but she figured that the dorms would be a great place for her to meet new people and make new friends.

She didn't seem the least bit nervous to be around the people on the campus, but at the same time, when they returned to the flat each day and made dinner, something seemed a little bit off about her, and Mark wasn't quite able to put his pawtip on it.

I swear...that's so weird. I know she showers every morning, but it's like she's stinking the place up somehow, Mark thought to himself, as he sat down at the dinner table with Tam. He was too polite a person to make any sort of a comment, and even then, he found the scent quite a bit to his liking, much to his dismay. It just felt weird to say that he enjoyed the scent of his sister, and it wasn't a foul stench or a body odor that she was producing. It was just something that he didn't have much experience with to recognize, and it was sure to get him into trouble.

Mark had taken plenty of girls to bed with him in high school, and a few already in the young university semester. None of them, however, had been in heat at the time, which was always to his benefit.

"Uhm...M-Mark...do you happen to have any spinach in the flat, by chance?"

Looking up from his meal, the Clydesdale was shocked to see Tam looking back across at him, but not with the kind of hungry gaze he was expecting. Her eyes were glazed over with something else entirely, and because of his slight naivety, he didn't seem to recognize it at first; at the very least, he was in denial about what he was looking at. "No, Tam...I'm sorry. I think the closest thing I've got is lettuce."

"That's okay. I've heard it would have helped, though..."

Her voice faded off at the end in such a way that even as Mark flickered up one of his sharp, thin ears, he didn't quite catch every word. "Help what? Are you feeling sick?"

"O-oh, no! It's nothing!" Tam hastily replied, not wanting to arouse any suspicion. "I've just heard that it's really good for you, and I...I want to be looking my best for the formal this year, that's all."

"Oh...kay..."

Mark raised a brow at his sister, not believing a word of what she said, but he didn't quite feeling like prying at the moment. At meals, he wasn't the most talkative person, and though he wasn't exactly a professional, he felt that he'd cooked up a rather impressive meal.

It was also making him just a little bit sleepy, and his sister was a handful to keep an eye on at the campus. "I think I really outdid myself this time, Tam, but I'm pretty sure I went a little too hard today, too. I think I'm gonna hit the sack early...feel free to watch my TV and play video games or whatever you feel like doing. I'll see you in the morning."

Still just slightly edgy, Tam managed a smile that looked a little less than nervous and nodded up at her brother as he stood from the table and walked away. "Sounds great, Mark. Sleep well, okay?" she bid him goodnight, and as he walked past, she shamelessly turned her head and stared, admiring the powerful muscles that ran down through his thighs and into his calves. She gazed up and down over him as though he were a model on the runway, and her sparkling orbs came to settle on his rump, filling out his blue jeans with a perfect, snug appearance that allowed her to see just how taut and firm his backside really was. She was licking her lips before he turned into his door and closed it behind him, and the moment she heard it click shut, she gave up on her dinner and hopped up, running to the medicine cabinet.

"Gotta be something...I had to miss something!" she cried in quiet panic, trying to keep her voice down as she scoured every single pill bottle she could find. "Can't freaking believe I mixed up my vitamins with estrus inhibitors...this is killing me!"

One paw stayed rummaging through the cabinet as the other paw snuck under her skirt and right past the thin, bikini cut of her panties. She tugged them aside hastily and began playing, allowing her pawtips to slide along the already soaking wet mound of her womanhood and explore her sex for what had to be the fourth time since she'd been at her brother's flat. She'd been able to do it in secret each time, but she kept getting closer and closer to being caught, and now, having been off of her medicine for four days, she'd be going into a full blown heat within minutes, with no amount of self-control to keep her from making a terrible mistake.

"Can't believe myself...looking at Mark like he was just one big, sexy hunk of man...the only man that can satisfy me...oh, gods...I n-need a cock!" she bit her lower lip, doing her best to keep the noise down as much as possible. She was suddenly very thankful that the flat had decent noise-proofing, as her ears could easily pick up the wet, slick sound of her pawtips fiddling along her labia and rubbing into the erect bud of her clit. There was something supremely erotic about the sound, and she was only turning herself on that much more as she looked over the last pill bottle.

There wasn't a single thing in the cabinet that would help her, and no foods that would prove as a natural remedy. She had no option but to go to her brother, and beg him for a ride to the pharmacy.

Wait...it's the damned weekend, and none of these places will have my name on file! She mentally panicked, wishing that she could come up with an answer for the cry of her loins. It'll be days before I'm able to get any sort of real help with this!

Tam was nearly doubled over the counter as her other paw scattered pill bottles to the counter and the floor, all en route to dipping two pawtips into her hungry, waiting snatch. Tiny drops of spittle flew from her maw as it opened and let out a nearly silent squeal of delight, but even with the powerful, sensual touch, there was something missing, and it kept her body burning with a need that could only be answered by a male.

She couldn't believe what she was doing. She felt as though she were outside of her own body, watching a short film of herself as she pulled her paws free and marched down the hall to her brother's room, knowing he'd still be awake. She threw the door open roughly and gained her brother's attention immediately, staring him down with narrowed eyes that blurred the line between sexual frustration, and downright need.

" Tam! What...what the hell was that for?"

"Wasn't sure if you were awake, brother mine," she replied, her voice taking on such a sensual tone that Mark couldn't believe it was coming from his own sister. "And I didn't want you to miss this..."

Pawtips glistened in the low light of Mark's personal TV as Tam slipped her paws under her skirt and yanked her panties down, allowing Mark to see the thin webs of her heated arousal that tried to keep her soaked underwear clinging to her body. Mark could feel his mouth open in a gasp all of its own accord, before his jaw simply dropped, every bit as slowly and drawn out as his sister's panties.

"T-Tam...you need to p-put those back on, right now, and g-get out of my room!"

"Sorry, but I'm afraid I can't do that until you get over here, pin me against this wall, and fuck my brains out."

No...shut up, shut up! Stop saying this! I need to fight it...I can't do this with my own brother!

Mark was a man of enough conviction to draw a line in the sand against what he thought was wrong, but true as that might be, Tam was plenty wet enough to wash that line away, if she knew what buttons to press. She didn't know what key it took to unlock the twisted treasures of his sexual mind, however, and thanks to that, he had just enough resistance to pull the covers down tighter.

"Sis...you are not in your right of mind. You need to go to your room and get some sleep!"

Tam rapidly shook her head. She rested both of her paws over her cunt and spread it open, pushing her hips forth so that Mark couldn't possibly ignore the sight of how much her womanhood drooled with strands of liquid need. "I'm not going anywhere until you fuck me, Mark...p-please, make this terrible heat go away!"

It was only at those final words that Mark realized where the earlier scent was coming from, and he felt stupid for not realizing it before. If he'd just asked, he could have helped her to get some pills to combat the urges, but now, he was faced with a decision...one that he couldn't make, even as his sister masturbated right in front of him, and her hooves carried her closer to the edge of his bed. He could nearly feel that extra wetness splashing against the end of his muzzle as Tam panted with need, and the bright blonde locks of her mane fell over her eyes, giving her an added layer of sex appeal.

Any man would have been crazy to say no to her right then...except a man of her relation, and Mark had just enough willpower to stand up and take advantage of her compromised position. " YES! DO IT!" Tam cried out, but as she felt her brother gripping her tightly, her ears flattened as she felt him lifting her up and literally carrying her out of his room. "H-hey, wait a damned minute!"

"Go. To. Bed. We'll talk about this in the morning," Mark ordered his sister, and the moment he put her down, he slammed his door and locked it...just hiding the arrival of a massive, throbbing erection. As he slumped down against it with a nervous, heaving chest, he could feel Tam beating on the door with closed, angry fists, until he finally heard her sobbing with frustration, and the door settled.

There was one last, thundering WHUD against the side of the door as Tam slammed both of her fists against it. "I will not be ignored, Mark...this...this aches...it hurts so fucking bad...I need someone to help me! P-please...just do it for me!"

Mark knew that his sister wasn't in control of herself...but that didn't make sleep any easier to get when he could hear her sobbing with sexual burden on the other side of the door, wishing that a man, any man, would douse the fires of her heat.

He just couldn't be the one.

**

Mark was lucky enough that Tam had cried herself to exhaustion that evening, and though he barely slept, he awoke to find her crumpled by the door, with her pawtips still fishing around in her panties when the morning came.

Groggy as he was, she was completely out, and it made it easy for him to lift her into his arms and place her in the guest bed, with the hopes that her episode was the extent of her outbursts. He made sure to leave a small note by the side of her bed, assuring her that he didn't judge her one bit, and that she was still just his innocent little sister.

Of course, the sexual thoughts of her that plagued his mind while he was in class made it hard for him to keep that image up. He couldn't clear the thought of her standing there in a schoolgirl outfit, lowering her panties and spreading her sex with such need that it stained his carpet; the scent was still there when he awoke in the morning.

"Looking terrible as usual, Mark," his professor said, as he was on his way out of his last class for the day. "Another long night of studying, I imagine?"

Mark shook his head. "Nothing like that, Mr. Wexler. My sister is visiting, and I'm afraid she's...come down with something."

"Oh, that's awful!" the professor admitted, showing a rare bout of compassion. "You could have simply told me so and provided a notice. I would have allowed you to tend to her today."

"No, sleep is the best thing for her right now...I'm hopeful that she'll be okay when she wakes up this afternoon."

Back at the flat, however, Tam barely slept in the guest bed, and the moment she was awoke, her jade eyes glazed over with an even greater need than the night before...and she knew just where to look to find what she needed.

"Come on, Mark...I know you've gotta be a kinky fucker. You always kept your little porn stash so hidden at home," she said to herself, remembering the first time she found a collection under his bed that was anything but vanilla. "What do I have to do to win you over...?"

Fingering herself the entire time she sat in his office chair, Tam bounced up and down upon the cheap furniture, allowing her wetness to seep into the material as she tried desperately to find any links on his internet browser. Nothing was really turning up, but she was plenty tech savvy, and knew how to find what was supposed to be hidden.

"Ctrl+F...let's see what kind of sick stuff you're hiding, shall we?"

She ran a search through every file on the computer, using all sorts of different key words to describe any fetish she could think of. A few different things turned up, but there was one that was far more prominent than the rest.

"Watersports...you sick little freak, Mark...you want me to pee myself? Want me to pee on you? Consider it done, big brother...I'll fucking soak you if that's what it takes..."

It seemed to be Tam's luck that Mark would turn up just in time to catch the end of her words, though he didn't catch the entire sentence. He was too busy trying to ignore the fact that he'd come home from class to see his sister bouncing on her fingers as if they were a sex toy, all while browsing his computer and getting the slick, sticky juices from her sex all over his keyboard and mouse.

"W-what...what the hell did you just say, Tam?"

"Welcome home, my darling brother...I was just browsing your computer here, and I've gotta say: you've got some top notch stuff on this thing! Not that I needed any extra inspiration, but...now I know what you're into, too...and I bet you're so into some of it that you'd even do it with your precious little sister...since, y'know, you're too good to fuck her, apparently."

"Tam, that is not...I mean, it's not like that! We can't do that! We're siblings! It's just wrong!"

"Is it wrong for a brother to help his sister in her hour of need?"

"W-well, no, but-

"Then I think it's about high time that you brought that thick, tasty looking cock over here and speared me on it!"

"I already said no last night, Tam, and that's the way it's gonna be! I...I just can't do that! I know you think I'm helping, but...we'd both regret it for the rest of our lives, and you know that!"

Tam spun around in the office chair, spreading her womanhood to Mark again and allowing him to see just how absolutely sopping wet she'd become. His chair was nearly soaked through, and excess streams of her juices spilled down her thighs as she grinned up at him, unable to keep her tongue from spilling out of the side of her muzzle. She was still lost to the throes of passion, and her heat had full control of her mind now, clouding anything that could be called "better judgment." Even if her heart of hearts knew it was wrong to sleep with her brother, her body was in full control of her actions, and her mind recognized that he was a male well worthy of ending her heat.

"I had a feeling it would take a little more convincing than that, Mark...so I've got an ultimatum for you."

"I'm not interested, Tam."

"That little bulge in your pants says otherwise...but I've got ways to get you on board, I think. See...I just learned about some of the stuff you're into, so here's the deal: I'm not gonna pee again until you get over here and fuck me so hard that this shitty little chair breaks underneath us!"

Mark gulped without thought. His immediate reaction was panic, and he couldn't possibly hide it. "Tam, how could you invade my privacy like that?!"

"Stop acting so mad at me, brother. I'm sure you haven't had a female who was willing to try this with you, yet. Bunch of stuck up cunts that don't know what they're missing..."

"That isn't the point, Tam! Just because I'm into that doesn't mean I'd do it with you!"

"Oh, I think you would with a little more convincing, Mark," Tam suggested, as she stepped up from the office chair, not having the patience for Mark to have out his mental battle. She needed to be satisfied now, and while watching her brother stand there with indecision was a bit of a turn on, she didn't need any further arousal. She just needed him to do what she thought was right, at least for the moment, and clearly, she had him in her grasp, if she played her cards right. "Wouldn't you just love to feel a sexy little slice on your lap, right on the verge of wetting herself while she grinds against your thick, throbbing cock?"

Mark felt like he might have walked into the set of a pornographic movie instead of his bedroom, but he certainly reacted like he was in the former. He froze up as his sister approached him, her hips swaying to each side just slightly as she sauntered up to his paralyzed figure. She admired him from head to toe, not letting an inch of his body go unappreciated, while licking some of the delicious arousal from her pawtips. Coated in a mixture of natural lubricants and her own spittle, she beckoned him to her with a crooked pawtip, but he stayed frozen...and his knees locked up.

It was the only chance Tam needed, as she jumped into her brother and knocked him over, straddling herself right around his hips with no regards for his safety. She wasn't heavy, and knew he'd be fine when he hit the ground with a rather solid THUD, only to look up and see his sister grinding her hips upon the bulge in his jeans.

"Take 'em off. NOW."

"Tam, we can't! I'm not gonna bend on this!"

"It feels like it's bending a little bit. Bet I could fix that if you took your pants off."

Mark groaned quietly, unable to deny his pleasure, but also shocked at how his sister's heat was making her speak and act. "You...you truly are insatiable, aren't you?"

"You have no idea, brother mine...and I'm about to burst...I can feel a little pee coming out...g-goodness, it's too much!"

"Tam, s-stop it..."

"Oh, but I can't! It's overflowing...oh, no...it's getting all over your jeans!"

Mark gritted his teeth together as he felt his sister's golden stream gently pouring out over the front of his jeans. It soaked through easily as the warmth came into contact with his cock, acting as the tinder upon which the last of his inhibitions burned.

"I felt that, Mark...I felt that delightful little throb against my cunt...you love this, I knew it! You want more...you need more, just like I do!" she cried out with delight as she released herself, allowing a warm, flowing stream of urine to spill forth from her body and soak her brother, making a fine mess of his jeans and going right through the boxers underneath. Mark gasped as he felt the forbidden liquid trickling down his pulsing shaft and over his sack, and in an instant, he was a broken man, hypnotized by the heat of his sister into making a terrible decision. "Ooooh, that's just so much better! I just love peeing on my naughty big brother..."

Don't talk like that, Tam...I'll...I'll end up...doing this...

Mark reached down between his legs and undid the buckle of his belt, still dripping with the spilled liquid of his sister. He struggled, but succeeded in unbuttoning his jeans and yanking down the zipper, and his sister went right to work, pulling his boxers down and letting his cock spring free, almost full in length, but still not quite soft. She watched it with eager, curious eyes as it grew stiff in front of her, and uncaring of the fact that she'd just peed upon it, she took the flared tip of her brother's horsecock into her mouth and swallowed her throat around it, drinking her own urine right off the tip.

"S-so...so damn hot...that's too fucking hot, Tam!" Mark tried to protest, but he knew that he was far past the point of no return. He couldn't believe what his sister was doing, but as impressive as it was to watch her swallow his length orally, it paled in comparison to the sight of her climbing up a little higher on his hips, until she gripped the base of his member and finally sat upon it, letting the wide flare of his member pry her soaking labia apart. She was already crying to high heavens when she slipped the whole of the tip inside of her body, and though seeing how wet she was stunned Mark, feeling it left him absolutely breathless.

He'd never felt anything like it. It was as though his cock was swimming in an ocean of pleasure, wrapped up in the tightest, slickest passage that he could fathom, and somehow, her every wall managed to clinch and cling to his member in a new way, each and every time that she bounced upon him. Her paws, shaking and desperate for a climax, came to rest upon his thighs as she tilted back and bounced her hips, taking every single massive inch of her brother's length inside of her and riding upon it with a knowledge that it was the only thing that could cure what ailed her.

"S...see? Such a p-perfect fit, Mark...your cock was made for me, big bro!" she complimented his impressive manhood as she bounced upon it, making sure to reach back and tickle the base of his sack every few seconds, wanting to milk the cum right out of him. "Nnngh... I think I'm c-cumming already, but...don't you dare stop, Mark...I wanna feel you pounding my s-sweet little pussy!"

The rapid, fluttering contractions around his cock were something that Mark knew all too well from other females, but without a condom, and in heat, his sister provided a pleasure beyond compare. Her sex was rapidly squeezing around his shaft without pattern, leaving him entirely off guard, no matter how hard he tried to prepare for it. He could feel his seed bubbling up in his sack and nearing the tip of his cock as Tam continued to fuck herself on it, having no desire, nor willpower to stop herself any longer.

Somehow, that made it even hotter for Mark, who was content to drown in the downright forbidden pleasure of the moment. He could feel the mixture of his sister's urine and slick arousal spilling down over his sack and tickling his every nerve, all while her body fought his for the cum that it so desperately craved. "T-Tam...oh...ooooh fuck, Tam! You need to g-get off of me...I'm gonna f-fuckin' cum!"

"I'm not going anywhere!" Tam shot back at him, gripping his thighs tightly and slamming her hips down with such force that she could feel her brother's sack bounce against her ass. "Every drop, brother...don't you dare hold out on me!"

This wasn't part of the plan for Mark, who was going to pull out...but his sister had him pinned, and her sex felt so amazing around his cock that he knew he could never pull out in time.

The gravity of the situation set in as his sack contracted around the sizable orbs within, and the flared head of his cock erupted inside of his sister, painting her inner walls with a thick, heated burst of his cum. " Tam! F-fuck yes!" he cried out, knowing that what he'd done was terribly wrong, but just like his sister, his body was dictating his actions. His hips slammed forward and hammered into her backside as he pounded his cock into her body as far as she could take it, and she threw her head back in delight as she could feel her insides being coated with the sticky mess of his seed. She lifted her paws to her breasts and squeezed them tightly, milking the last of the pleasure that she could out of her body as she felt his flow subsiding, and even then, her hips continued to bounce, uncaring of the wet, sticky mess that she was setting herself in.

Might steal a little more of his cum that way...probably knock me up...what a good big brother... she thought, as her mind was entirely poisoned by the arousal of her heat. She panted heavily and gazed down upon the exhausted Clydesdale, her eyes narrowing on his own in such a way that he knew this was only to be the first round.

"Tam...g-get a hold of y-yourself," Mark finally called out to her, as he tried to catch his breath. A quick, sudden and intentional squeeze from his sister's inner walls quickly shut him up, however, as he gritted his teeth together in delight. "Ooooh gods that's good..."

"I've got a hold of the only thing I want, r-right here," Tam replied, as she gave his member another internal squeeze. "And you're not going a-anywhere for a while, brother mine...we're just getting started."

Mark could already picture the fruits of his seed swimming up into his sister's womb, and he knew that it was already flooded with his cum...but his cock stood stiff and defiant against his better judgment, and Tam was grinning wickedly as she lifted her hips again.

"Give me your babies, big brother...fill up my womb and make me a proud mommy..."