His Sister's Girlfriend

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He is asked to be his sister's sperm donor.
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angstboy
angstboy
59 Followers

"Okay," said the doctor, holding James' erect penis in her hand and slightly stroking it to keep it hard. She winked at James. "Your ultrasound shows your cervix is 12" from your vaginal opening, Sarah. That's a little high, but you're also a tall woman, so nothing to be worried about."

Sarah lay on the doctor's table with her legs in the stirrups, holding James's sister's hand, clenching as if for dear life.

"You're sure?" she asked, a note of anxiety in her voice.

"Of course," Dr. Madison smiled. "Especially since James is significantly larger than the average male, I don't think it will be a problem at all."

The doctor pulled a pen out of her pocket and made a small mark on Sarah's stomach. "This is roughly where your cervix is, James, come forward."

James shuffled forward, Dr. Madison's hand still gripping his rock hard cock. The doctor guided him between Sarah's legs, letting him go with a long caress from base to crown.

"Now James, I want you to place your penis on Sarah's stomach, so that your testicles are just touching her vaginal lips, that should approximate full insertion."

James did as the doctor told him to, enjoying the feel of Sarah's taut stomach underneath his cock as he shifted slightly to line himself up. He could feel her pussy lips against his balls, warm and still slightly moist from the lubricant they had used for the ultrasound. His cock reached almost to the dot on Sarah's stomach, perhaps an inch or so away from it.

"Excellent," Dr. Madison said. "Now we do want to be certain that his ejaculate will reach the cervix, so James, could you perhaps masturbate for us now?"

James pretended to be surprised. He had planned this out for weeks now, ever since his sister Alex and her partner had come to home to ask if he would be a sperm donor for them. James had always had a crush on his sister's girlfriend. He didn't like the word, but since it had started when he was sixteen it had seemed appropriate at the time. Even in high school Sarah had been gorgeous, and now that she was 21, her body had come into its own. Her breasts were large, easily an F cup, and she and Alex had joked that the only person in school with tits larger than Sarah had been Alex. Other than that, the two women were almost complete physical opposites.

Alex had always been terrified of becoming fat (although James didn't know why, their mother and two aunts were both in great shape), and as a result had spent almost every day of the six years since her 16th birthday dieting and at the gym. Her arms and legs were muscular, she could almost be described as ripped, and her stomach was flat and solid as a rock. Even her ass was toned, and James' had spent many a night stroking his large cock and thinking about sliding it into his sister's amazing tight ass. Her blond hair was currently cut short, framing her elfin features as she held onto her partner's hand.

Sarah was not as concerned about her appearance as her partner was, and although she stayed in shape, maintained a smooth curvy figure. Her red hair set off her tanned skin (just because she didn't go to the gym religiously didn't mean she didn't get outside and stay in shape), and she often wore low cut shirts to show off her breasts, which she once joked were the only reason she had gotten through college. Josh suspected the fact that her hair helped, too, which she always kept long and was a lustrous, curly auburn, which Sarah said came from her Puerto Rican relatives. She also had a tendency to wear tight pants rather than dresses, which Josh figured was to show off her incredible ass as much as it was for comfort. Where Alex's ass was tight and toned, Sarah's was full and round. James had probably spent as much time masturbating to Sarah as he had to his sister, perhaps more. When the two girls had hooked up in college, he had probably masturbated to fantasies of both of them at the same time even more.

Now, if he was careful, he might be able to bring that fantasy to life. And even if he wasn't careful, he would get half of it. He slid his hand around his cock and began to stroke it, trying to shut out the image of Sarah's lush sexy body laid out in front of him. After a few minutes, he shook his head and turned to the Dr. "I'm sorry, doctor, I don't seem to be able to do it right now, this is all a little weird for me."

Dr. Madison nodded. "I understand, perhaps we could add a little bit of mood? Sarah, Alex, would that be okay with you?"

The two women nodded, and Dr. Madison turned to dim the lights a little bit. "Perhaps, Sarah, you could take your shirt all the way off?"

Sarah looked surprised. "Do you think that's necessary, doctor? I mean, we're only doing this for the insemination?"

"I understand, Sarah," Dr. Madison replied, "But you do know there will be multiple sessions at home, this is simply to make certain everything is going to, fit together, so to speak. And there are a number of studies that show that the more excited a man is, the higher his sperm count, so I would recommend that you do your best to excite him at home as much as possible. We may as well get you used to it now, right?"

Sarah nodded. "I suppose that makes sense, what do you think Alex?"

Alex jumped. She had been quiet for most of the visit, and had said nothing since James had gotten undressed at the doctor's request. She had always known her brother was large, the girls in school had gossiped of course, but she had not been expecting the baseball bat he had displayed. And when he had lain its length on her partner's stomach, she had been unexpectedly turned on, and, for some reason, jealous. She had barely heard the request, she had been focused on her brother's large cock laying on her lover's body, imagining what it would feel like sliding into her. Into Sarah that was, not herself.

"Of course," she said, "I think the doctor knows what she is talking about."

Sarah released Alex's hand for a moment and slid her shirt off over her shoulders. Her breasts almost overflowed her bra, even laying down on her back.

"Yes, your brassiere, too," the doctor instructed.

Sarah unclasped her bra from the front and shrugged out of it, the movement making her large breasts wobble sexily. James almost forgot himself and tried to grab one, but held himself back. That would come later, he knew, for now, he just had to let Dr. Madison take the lead.

"Excellent," Dr. Madison said. "James, is that helping?"

"Yes, doctor," he replied dutifully. He wrapped his hand around his cock and began to stroke again for a few minutes before turning to her. "I'm sorry," he said. "I just don't think I'll be able to cum from stroking myself." He laid his cock back on Sarah's stomach, enjoying the feel of her skin against him.

"I understand, James," the doctor said. "Perhaps you could use some assistance?"

"I think that might help, yes," he said.

"Well, then," the doctor said. "I suppose I could help out this time."

Dr. Madison move to stand beside him and reached around to grab his cock at the root, pressing her breasts into his back. He almost came at that point but held desperately on, the combination of his sister's girlfriend's stomach and pussy rubbing against his cock while Dr. Madison's full breasts pressed against his back almost driving him over the edge. She began to rub her hand up and down his cock along the top, curling her fingers to make it look to Sarah and Alex like she was actually stroking James, but not actually disturbing where it touched Sarah's body. Even without the direct stimulation, the butterfly caress of her fingers along his cock made precum start to drip from the tip and pool on Sarah's flat stomach.

Alex was transfixed, watching the doctor's petite hand stroking her brother's massive erection. She could not believe that watching someone stroke a cock, her brother's cock no less, could be so exciting. She had given up on boys on high school and thought she had never looked back, but something about the animalistic power of the giant member sticking out of her brother's groin, and the taboo fact that it was her brother's was combining to send chills down her spine, directly to her pussy. She didn't want to admit it to herself, but she knew that later tonight she was going to be thinking about her brother while she was making love to Sarah.

"Ah," Dr. Madison almost purred from behind James. She seemed to have pitched her voice just a bit lower and more breathy. "You see the pre-cum? We have an urban myth that that can't make you pregnant, but I can tell you that in fact, the sperm concentration can be higher in pre-cum than in the regular ejaculate. I would suggest in your future endeavors that you make certain you don't miss anything, so be sure to insert the penis as quickly as possible into Sarah's vagina, do you understand?"

Sarah had already been turned on by the feeling of James' huge penis resting on her stomach and his balls against her pussy, but the sound of Dr. Madison's voice sent a thrill through her, and she was embarrassed to realize that her pussy was wet. In fact, it was dripping almost as much as James' cock was, she was so turned on. She nodded quickly at the doctor's question, trying desperately to follow her words as she fought off the odd sensation of being turned on by a man, telling herself it was okay because he was going to be their sperm donor, and that it was really the doctor she was responding to. Either way, she knew she was going to be thinking about this tonight when she fucked Alex. And she knew at this point, she was so turned on she was going to fuck her partner's brains out.

"In fact," Dr. Madison continued, "I think we should practice that right now, just to make certain that everything will work smoothly, don't you Sarah?"

Sarah nodded again before she realized what the doctor had just said. "Practice?" she said. "You mean...?" She trailed off, realizing that as soon as James moved his cock to her pussy he would realize how wet she was, and so would Alex, for that matter. She didn't know which made her more embarrassed, or excited. She struggled to find a reason to avoid that situation. 'But, I don't know if I'm ready, I mean at home we have lubricants prepared -"

"Oh, I don't think that will be a problem," the doctor cut her off. "Alex, why don't you give your partner some assistance, what usually excites her?"

Without even thinking about it, Alex responded, "her breasts. Sarah's breasts are very sensitive."

"Ah, excellent," the doctor said. "Then we won't even have to shift positions. Sarah, you know your partner's body, why don't you just do a little manual stimulation there, and we will prepare for the insertion of James' penis?"

Sarah wanted to say something, but before she could think of another excuse, some way to prevent James from finding out how turned on she was, the doctor had taken a step back and James had shifted his hips to place the head of his penis at her pussy. Alex had moved behind her head so that she could caress both of her breasts at the same time. Alex had been right, of course, she knew her partner's body almost as well as her own, and her breasts were incredibly sensitive. Shivers ran up and down her spine as Alex caressed Sarah's breasts, gently at first, running her fingernails around the outside and the incredibly sensitive skin underneath. Oh my god! she thought, this is incredible! I can't let myself enjoy this too much, this is just for medical reasons, this is just so I can get pregnant.

Meanwhile, James had begun inserting his cock into Sarah's pussy. He had noticed she was already dripping, even before his sister had begun stroking her breasts, and he smiled inwardly to himself. He was actually going to make this work, he thought, he was going to fuck his sister's girlfriend. Dr. Madison had moved out from behind him and now stood at Sarah's side. "I think we might want your legs spread just a little wider, Sarah," she said as authoritatively as possible. "Let me make a quick adjustment."

Before Sarah knew what was happening, another pair of hands was now stroking her legs, the doctor's fingers running up the insides of her thighs. Oh fuck, she thought, if I wasn't going to come before, I am definitely going to now! The doctor, ostensibly shifting her thighs apart, was also allowing her fingertips and nails to caress Sarah's thighs as she did so, and the combination of that and her girlfriend's stimulation of her breasts was about to drive her crazy. She could feel her pussy had gone from wet to dripping like a faucet, and James slowly and easily slid the length of his cock inside of her, burying himself to the hilt.

Sarah had never felt so full before in her life, every nerve inside her pussy was on fire, responding to the incredible length and girth of her partner's brother cock inside her. Alex's touch on her breasts had become more insistent, her partner's nails now rubbing her skin and raising goose bumps all over her body, while the doctor's caresses of her inner thighs were making her legs shake from excitement. She desperately did not want to come while being fucked, did not want to admit that a cock inside her like this could feel so good, but the stimulation of her entire body was not going to let that happen. The best she could hope for was that she wouldn't give away to James how much she was turned on by his penis inside her.

James leaned forward slightly, pressing his stomach up against her, the base of his cock now rubbing up against her clitoris. She was so turned on he could feel it pressing against him, and he pretended to shift his weight and rubbed himself against her again, feeling her legs shake as her clit responded to his action.

"James," Dr. Madison said, never letting her hands stop moving up and down Sarah's thighs. "Let's make certain that everything is working smoothly, why don't you make sure you have decent freedom of movement. I have to imagine that Sarah is quite tight, especially given how large your penis is, correct?"

James nodded. "Yes, doctor, I can feel her holding me tight."

For some reason, Sarah felt inordinately proud at James' statement. Although she was not Gold Star, she had definitely had limited experience with men, and she was glad that her pussy was still nice and tight. Underneath that was also pride that she was making James feel good with her pussy, since he was making her feel so good with his cock inside her. It's because he's Alex's brother, she said to herself. I am just happy because they are related, that's all. He' like half of Alex, right? So fucking him - oh my god he fills me up - is like fucking her, it' just like fucking Alex, that's all. Then the image came into her head of fucking them both at the same time, a wicked and hedonistic threesome with the brother and sister both pleasuring her and themselves. She tried to not indulge in that fantasy, tried to push it out of her head, even as Alex moved from the outside of her breasts to grab her nipples and start to squeeze them, sending even more flashes of pleasure through her body, up into her brain and down into and through her pussy. For a moment she thought she was going to black out, the pleasure was so intense, and then James shifted his hips, moving his cock out. He was so large, it was like a never-ending sensation as he moved his hips backward inch by inch.

"Please," she whispered as she felt the head of his cock at her entrance, not even knowing what she was referring to. She wanted to think she was asking him to stop this absurd act, but she knew she wasn't. She knew, even if she couldn't admit it, that she was asking him to put it back in. Begging him to slide his incredible cock back inside her pussy, to fill it up and stretch her out, to claim it as his. She bit her lip to prevent herself from saying, or shouting, anything else, and instead simply let out a small whimper as James began the long slow slide back inside her.

When his hips pressed against hers, she couldn't control herself however. Her breasts, her legs, her pussy, every inch of her was on fire, stimulated beyond her control. She bit down so hard on her lip to keep from crying out in pleasure that she tasted blood, but it could not prevent her intense orgasm, starting from the bottom of her toes, making her legs shake as it passed up her body, bucking her hips and making her breasts bounce in Sarah's grip as she shuddered and quaked, coming over and over again in response to James fucking her, to Alex playing with her breasts, to the doctor massaging her thighs. Her pussy spasmed again and again around James' cock, each contraction milking his cock, sliding her sensitive inner flesh back and forth across his incredible cock and setting off another explosion. The pleasure was so intense she blacked out for a moment, stars shooting through her vision.

Sarah reached out to grab Alex's hair, and Alex was surprised as her girlfriend dragged her into a deep and passionate kiss. Seeing Sarah so turned on was overpowering her own willpower, and feeling Sarah's soft tongue thrust into her mouth caused her own pussy to start dripping. She had already been excited watching her brother's huge cock impaling her girlfriend, imagining that it was entering her own pussy, and playing with Sarah's breasts at the same time had already turned her on so much she was a little worried she would attack her own brother and force him to fuck her. Now with her hands still kneading Sarah's breasts, the incredibly sensual feeling of her girlfriend's generous orbs overflowing her hands, and feeling Sarah's body buck and jerk as she obviously orgasmed over and over in response to Alex's own brother fucking her, Alex did the only thing she could to address her own overpowering urges, and removed one hand from Sarah's breasts, ignoring the woman's slight whimper, and it down into her own pants, desperately diving through denim and her cotton panties to find her own clitoris, grinding the palm of her hand against it while she slipped her middle finger into her own tight pussy, relishing how easily the digit slipped into her dripping wet pussy.

Again, knowing that that night she was going to fuck her girlfriend desperately while thinking about her brother's cock, and so overcome in the moment that she didn't even care, all she could focus on right now was the feeling of her finger in her pussy, her hand rubbing her clitoris, desperately bringing her own explosion of pleasure. She almost fell over as she came hard, the only thing keeping her upright were Sarah's hands gripping her hair, still forcing her tongue into Alex's mouth, and her grip on Sarah's large breast. Squeezing tightly to keep from falling over set Sarah off again, the redhead's hips bucking like she was trying to throw James off, but his cock remained firmly embedded within her.

Unnoticed by Alex and Sarah both, Dr. Madison gave up any pretense of medical professionalism and leaned over to suck and lick Sarah's clitoris while James continued his slow and careful fucking of her pussy, now arching his back slightly to give the doctor room to orally pleasure his sister's girlfriend while he fucked her. Sarah had just come down from her third or fourth intense orgasm, she had lost count, when she felt the warm wet mouth of the doctor descend on her pussy at the same time as Alex gripped her breast tightly and she could feel her girlfriend's arm moving. Knowing that Alex was fucking herself allowed Sarah to finally give up any worry or self-control and surrender to the pleasure that had been building like a skyrocket and she came again, even harder than she had before, harder than she ever had in her life. She felt like she was drowning, and floating, and bursting into flames while being dowsed with water all at the same time.

Her back arched, her breasts desperately seeking more contact with Alex's hands, her clitoris desperate for more contact from Dr. Madison, her pussy desperate for more of James' cock. She felt every muscle in her body contract and relax and then contract again, her eyes rolled into the back of her skull and a long and loud gasp started in her throat, leading to a loud moan as she gave in to the sensations, knowing that she was being pleasured by three people, the center of their sexual attention and loving every moment of it. Then James came, she could feel his cock expand, getting thicker and filling her up even more, more than she could have imagined possible, and she felt every jet of sperm shoot out from his cock, coating the inside of her womb, shooting over and over again, every spurt making her come again, and she screamed in pleasure, not even trying to pretend like she was not enjoying this, enjoying being fucked by a big cock, that this was what she needed, and what she would need over and over again for the rest of her life.

angstboy
angstboy
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01Timber6701Timber6710 months ago

Ok ,,, first off 2⭐️ for the following reasons,,, 12 inch cavity,,, sister girlfriend,,, doctor involved and in the office to boot ,,, so how does this fit into this category

ScottishTexanScottishTexanabout 1 year ago

How old are you? Twelve? This story is nothing but juvenile bullshit. 😒

I loved the idea of a lesbian sister asking her brother to impregnate her girlfriend by natural methods, but you totally failed with the 12 inch deep vaginal cavity and big dick to match. 1/5

MiniwandMiniwandover 3 years ago

Because it doesn't have any more chapter, I put one star. Exciting story but very short. I would have loved to read how this situation came to be and what happens next. With just this, it's a disappointment.

AnonymousAnonymousover 3 years ago
Weird Ending

I Liked the Story but not the ending

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