Being My Sister's Sperm Donor

This will be the first of a series if it's well received. Thanks to dpga4625 for the editing.

*

"You can't be serious," I asked astonished.

"Of course, we are, we discussed it thoroughly, and we think it's the best option." my sister Sarah answered, smiling at her wife.

Sarah and her wife Amy were both twenty-one and had been married a year. They wanted a baby. My sister was infertile, so they decided Amy would carry the baby. I got that, what I didn't get was why they wanted me to donate the sperm.

"It's too strange. I would be their uncle and biological dad that's nuts." I asked exasperated.

"Don't worry Adam, we won't tell them until they are old enough. You don't have to do anything, just be their uncle," explained Amy.

"Except impregnate my sister-in-law," I pointed out, they both laughed.

"You just need to give a sample you guys won't need to, do, stuff" Sarah laughed.

"I don't know Sarah, would be cheaper" Amy giggled, looking me up and down.

"Haha," I said sarcastically.

My sister-in-law had always teased me since were kids. We grew up together, they were a couple of years older. Amy was my first crush, something she was well aware of and tormented me with. She was my sister's best friend who had been in love with her since she hit puberty. It took Amy a string of shitty relationships and one girly weekend in Paris to realize she loved my sister too.

"I just don't see why it has to be me," I said reasonably.

"You know I have always wanted to carry a child, finding out I couldn't was devastating. With Amy's egg, they will have half her genes and we don't want the other half to be some, random guy." Sarah spoke with such passion and vulnerability.

I knew how much it had hurt her to find out she was sterile I was with her in the hospital.

"What about the neighbors, friends' family, what will they say if they found out," I said concernedly.

"All they will know is we're using a sperm donor, when it comes time to tell our baby we will judge the situation," Sarah said convincingly.

"I'll think about it," I said. They both came over and hugged me. My sister and I were pretty tactile, we always hugged and kissed on the cheek. Hugging Amy was different, I felt her warm body and pert tots pressing into me and my cock stirred. Thankfully I don't think she noticed.

In fairness, I could understand the reasons why they wanted my sperm. My sister did look a lot like me. We both had chocolate brown hair, our mum's dark brown eyes and dad's nose. There were differences to of course. I was tall, where she was short. I had a few pounds to lose. She had the tight toned body of an athlete.

Amy was a tall leggy blonde, she looked like a Swedish volleyball player. She had a pert, full bum, blue eyes and luscious breasts, a good handful each. It's a bit sick but I often thought of them fucking. Imagining Sarah camped between her wife's long supple legs, sucking on her swollen clit was a regular, in the fantasy wank bank. I had come to terms with my perverted fantasies, after all, they were only in my head.

I didn't know what our parents would think about all this, but they had died in a car crash five years ago. It was the same crash that caused Sarah's injuries resulting in her infertility. We got through it together. I was only fourteen, Sarah was sixteen. It brought us together. Our grandmother moved into our family home and looked after us until we were old enough to look after ourselves. Now it was just Sarah, Amy and me.

I had no one from whom to ask advice. I didn't want to ask friends in case they judged my sister. I mulled everything over. I loved my sister; they would be amazing mothers. I also like the idea of being an uncle, this would be an amazing gift for them. I don't know how I would feel watching my child grow up, pretending I was their uncle. Would it affect the dynamics between my sister and I? In the end, I decided to help as my sister, was a very special person to me. Since the accident, we had grown so close and I realized I would do anything for her.

They both cried when I told them. The trip to the consultant was nerve-racking. He explained everything and asked me loads of questions. My sister had taken Amy's name when they married, so we didn't have any problem with awkward questions. The consultant was concerned about my age. At only nineteen, the he grilled me to confirm I understood exactly what I was agreeing to.

Once we had signed some forms, he explained that they needed a sample today to test my fertility. I looked sheepishly at my sister and sister-in-law. They tried not to laugh as I was led down a corridor, by a very attractive young nurse to a little room.

"Here you go, just fill this to the top, you'll find some stimulating material in the corner." the nurse said passing a small pot to me. If was more confident I might have made a joke but I was nervous. I stood there hovering on the threshold.

"Come on, it's nothing you haven't done, thousands of times before." the hot young nurse whispered in my ear.

I walked into the room and heard the door click behind me, it was a grim place, clinical like a dentist, smell of disinfectant and cleaning fluid didn't help turn me on. There was a plastic chair, with a little table stacked with a variety of porn mags which I sifted through finding a page that piqued my interest. Two attractive young girls, one blonde and one brunette were kissing in a loving embrace.

It was easy to use this image as inspiration to draw on something from my wank bank. Girls in the image morphed into Sarah and Amy instead. The thought that they were both just a few meters away, and knew what I would be doing in here, made my cock grow.

I imagined them coming down the corridor and seeing if I needed any help. The scene played like a porno in my head. Sarah came in asked if I was having some trouble. She would then bring in Amy. They would seductively undress each other. I started stroking my cock at the fantasy.

Amy would give my sister a fiery kiss pushing her naked body against the wall. I imagined Sarah's back arching as the cold surface touched her bare skin. Amy would slip a nipple into her mouth and her hand glided down Sarah's flat toned stomach. Her tongue flicked out across Sarah's nipple, she pulled into her mouth and her puckered as she sucked on it. Amy's hand stroked Sarah's thighs slowly tracing circles, moving steadily up to her hot shaved pussy.

I felt the usual sensations building at the base of my cock. I just had enough time to pick up the beaker and deposit a sample, a big sample. There was a knock on the door,

"Hi, how's it going in there?" came the voice of the hot nurse.

I sorted myself out and opened the door. I gave my sample over and went back to the waiting room. Amy and Sarah looked over as I entered making it a bit awkward waiting; I couldn't make eye contact with them. A short while later the consultant called us into the office. I had good swimmers, the girls hugged and kissed my cheek which was embarrassing.

Everything was going great, every month I would produce a sample and Amy would be inseminated at the clinic. After six months Amy still wasn't pregnant. It cost a lot of money each time and they were running out of savings.

"Maybe we should just have a break for a bit," I said one evening as the three of us had dinner.

"We don't want to wait Adam, I don't think that will help," Amy said.

"What about a different donor, maybe we're just not compatible," I said looking at Amy, she shrugged.

Sarah hadn't said anything all dinner, she just sat there playing with her food.

"What do think Sarah?" Amy asked putting a hand on her arm.

"I've been thinking maybe it's not you guys, you're both super fertile," Sarah said quietly.

"It's the clinic, that's the problem. I have been thinking, maybe we should go old school." Sarah looked at Amy earnestly.

"I love you, but I'm not shoving a turkey-baster up there honey," said Amy as we both laughed.

"No, I meant old school as in biblical," Sarah explained over the laughter.

Amy and I were shocked into silence. We made eye contact with confused expressions; Sarah was looking sheepishly at us.

"Wanna run that one by us again honey," Amy said holding Sarah's hand.

"Maybe you two should... You know, try conceiving naturally." my sister said.

"Wait, you want me to make love to your wife?" I asked still confused.

"What are you a sixteen-year-old girl? No, I just think it might be an idea for you to donate, straight to the recipient" Sarah said seriously squeezing Amy's and checking her reaction.

Amy's brow furrowed in thought. "It's an idea I suppose." she whispered.

"Hang on," I said exasperated, "This situation is weird enough as it is without that. Anyway, you know how jealous you get Sarah. I was around to see you seething every time Amy had a new boyfriend." I reminded them.

"It would just be until she gets pregnant, you're not bloody dating, I'm not wanting you guys to fall in love for fuck sake," Sarah said getting angry.

Amy chipped in with a suggestion. "Why don't we just tie him up and use him as a sex toy." she looked over at me seductively. Then started laughing again.

"That could work, we could blindfold him," Sarah said thoughtfully.

"No," I shouted forcefully. "I'm not being used as a sex toy, I'm not a prostitute!" This was started to get out of hand.

"Oh, honey don't worry, we weren't going to pay you," Amy said jokingly.

"I might not even be able to get hard with you anyway," I said waspishly, Amy's eyes widen for a moment, she was a little hurt and fell silent.

"Shut up Adam, you've fantasied about fucking Amy since you were twelve," Sarah spat back.

Amy tried to defuse the tension before it got out of hand. "Why don't we sleep on it, we'll talk about it again tomorrow night Adam." She took Sarah's hand and they went to their room. I tidied up and then went also went to bed.

We still all lived in my parent's house, I planned to find a place of my own after university. Amy and Sarah had moved into the big master when they got married. I often heard them fucking through the wall which is what inspired my wank bank fantasies.

Tonight, all I heard was muffled talking. I couldn't hear everything they said, but it sounded like Sarah was trying to convince Amy to agree to the idea. I tried to get some sleep, but half an hour later I heard the familiar sounds of sex coming through the wall. Amy was always pretty vocal and they followed a similar routine every time. Amy could be heard moaning as Sarah went to work pleasuring her.

I felt my cock harden as I imagined what Sarah was doing to her. Sarah's sexy pink lips, kissing up soft thighs as her fingers probed Amy's wet pussy. My hand slid down to my boxers and started to stroke my growing cock. Amy was moaning loudly, I imagined Sarah was now licking her pussy. Flicking her tongue across her swollen clit and fingering her tight entrance. They would soon move to the next stage, as they did every time they fucked. There was a break in Amy's groaning then the bed started squeaking. I imagined Sarah, naked wearing a strap-on, positioning herself behind Amy's sexy little bum.

Sure enough, a few moments later, I heard Sarah say, "You like that cock don't you, mmm it feels so good in your tight pussy."

"Yes, fuck me with that big cock, harder, like that, fuck it's so good," Amy groaned.

I was pumping my fist up and down my hard shaft. Trying to match the sounds of Sarah's thighs slapping on Amy's ass, as she pumped her fake cock into her. I was getting close to coming when I heard something new, something that made me pause mid-stroke.

"That's it baby you like my brother's cock don't you, you want him to cum in you. Oh, he wants your tight snatch baby. He wants to fuck you so bad." Sarah said breathlessly.

They had never said my name during sex before. This was weird. Amy's moans deepened. Then she said hurriedly. "Yes, yes, fuck me, Adam, make me cum. Your cock is so big, cum in me, Aghhh!! Harder, harder"

I had never heard Amy like this. I couldn't help but pump my cock faster imagining it sliding into her tight pussy. I heard yelps as Sarah slapped Amy's ass as she fucked her. I was so close.

"That's it, there, there, I'm cumming, oh fuck I'm cumming. Cum in me, cum in me Adam, ohhh FUCK!!!!!," Amy screamed at full volume as she orgasmed.

I sent spurts of cum all over the place. Ribbon after ribbon. A few moments later. I heard Sarah's voice. "Night Adam, sweet dreams,"

_._._._._._._._._._._._._._._._._._._._._.

I avoided the girls over the next few days. I was mortified that they knew I was listening. On Friday evening there was a knock on my bedroom door.

"Adam, sweetie, can we come in?" Sarah asked.

When I didn't answer they both came inside and sat in my bed. I couldn't help but notice they we wearing very short pajama tops, and very small shorts. Amy's nipples were poking through the material.

"We're sorry about the other night." Amy said smiling as she caught me looking at her nipples. I whipped my eyes away and stared at the bed.

"Yes, sorry sweetie we got a bit carried away." Sarah said with a laugh. I kept my eyes down and didn't say a word.

"Come on Adam." Sarah giggled putting her hand on my knee, "we had to listen to Rebecca Ferguson screaming through the wall all last summer."

I smiled, had been a very physical relationship, which fizzled out quickly.

"You didn't hear your name called, screamed through the wall though." I laughed, the tension between us all releasing.

"No, we just got a bit carried away after mulling over Sarah's idea." Sarah said eyeing my reaction. "I don't suppose you have thought more about it, have you?"

It had been hard to think of anything else. Every time I closed my eyes, imagined poisoning my hard cock into Amy's hot wet pussy. I hadn't thought at all about the consequences. The reality of having sex with my sister-in-law. "No, I haven't, I know this is important to you, I just need some time to think about it." I said fairly, looking into both of their eyes.

"Ok, that's good why don't you take the next week to mull it over, we can discuss it again next Friday at dinner." Amy said reasonably, taking Sarah's hand and leading her out of the room.

If I had hoped the girls would leave me alone, to think about things without influencing my decision, I was sorely mistaken. Sarah seemed to have found a willing accomplice in Amy. She wore her smallest, tightest clothes around the house. Torturing me at every opportunity. She would brush past me in the corridor, ensuring any contact between us lingered. She started hugging me and kissing my cheek when we met just like Sarah did. She even started doing Yoga in the living room in just a sports bra and shorts. The most blatant attempt at coercion came when Sarah asked me to grab something from their bathroom.

I walked in and my jaw dropped. Amy was standing in front of me, an exquisite naked body glistened with water after her shower. One leg was raised on the side of the bath as she toweled herself dry. She had music playing so hadn't heard me enter. I drank in her perfect form, I stared at her long slender legs, I saw her hot little pussy, I guessed she had just shaved she was so smooth. Her breasts were exquisite, a perfect handful each with light pink nipples. I don't think Amy was consulted on this particular attempt to convince me, when she saw me staring, she screamed and grabbed a towel to cover herself. I ran out of the room blushing. Sarah got the cold shoulder from both of us all evening.

Every night they fucked, very loudly and passionately. They refrained from calling my name out again. Instead, they made a show of using a strap on and narrating their activities in great detail. Friday night loomed and I needed to make a decision. We had a small dinner and then sat on the sofa in the living room.

"So, I have been thinking it over, if it's really what you both want, I'm in. But I have some conditions." I said taking a serious tone.

"First, I'm not an implement, nor a sex toy. I will not be blindfolded and used. Second, we don't let this change anything between us all." I looked over at Sarah particularly at this.

"Agreed," said Sarah, holding Amy's hand. "We have some conditions too. You don't kiss, this arrangement carries on until Amy is pregnant then stops, and you two are only to do it with everyone's knowledge."

I looked into both of their eyes. They were pleading with me to accept, they wanted this so badly. "Agreed, so when do we get started," I said trying to mask my eagerness. The girls laughed

"Down boy, I'm the most fertile starting tomorrow night, so we can get freaky then," Amy said giving me a wink. That night in bed, the girls gave another rousing performance, this time both screaming my name as they came. A strange thought occurred to me. Would Sarah listen to and Amy and I fuck through the walls and would it turn her on. I realized a dark thought, it turned me on.

_._._._._._._._._._._._._._._._._._._._._.

There was a nervous tension building all day. I spent as much time out of the house as I could, thinking about what was to come later. I got a text from Sarah asking if I was alright. I assured her I was ok, just nervous. She said she was too. I asked if we should just get plastered drinking rum, she explained that would likely reduce the chances of conception.

We had a nice meal together, the conversation was a bit muted, when I couldn't take the tension any more, I asked, "So, any thoughts on how we're going do to this, you know how to get started?"

Meeting both girls' eyes, I noticed Amy looked a little sheepish, which surprised me.

Sarah look at me thoughtfully and said, "I thought about it and think I should be the one to set things up, as I'm like the gooseberry here."

Amy and I both laughed a bit at that. "I think you should both go into our bedroom, turn the lights off so it's pitch black and strip. Getting naked is going to be the hardest part. Then feel for each other in the dark and get it done." Sarah said instructively. "Once you've done it the first time, I'm sure it will get easier. Just relax and try to enjoy yourself. There's a much better chance of this working if your both relaxed and you never know, this might not be the only time we need to do this." Sarah said all this with a smile trying to lighten the mood. She left the room and went upstairs to sort things out.

Amy and I were avoiding eye contact. She looked nervous, twiddling her hair and biting her lip. I found this strange, Amy usually seemed so confident, always teasing and flirting. It was odd to see her so timid.

"Right then we're ready," Sarah said enthusiastically as she came back down. I stood there self-consciously. She walked over to me held my hand, and lifted my chin to make eye contact.

"I love you bro, and I'm so grateful for this. Whatever happens, I love you. If you're not happy at any point, we will stop. You're more important to me than anything." Sarah spoke with sincerity placing her forehead against mine.

"Ok, see you in a sec," I said to Amy more confidently than I felt. I turned and walked upstairs into the master bedroom.

The room was in complete darkness. Sarah had blacked out all the windows, every crack. I guess she would be giving Amy a prep talk. I decided to get the ball rolling and strip off naked. Standing in the pitch blackness was somehow comforting. I lay in bed under the sheets and waited. I absentmindedly started rubbing my flaccid cock to try and help it on its way.

The door opened slowly and in slipped Amy. She wore a silk dressing gown and nothing else. "Love you guys, I'll be next door if you need me," Sarah said at the doorway. When she closed the door, we were left in complete darkness again. I heard movement as Amy shuffled over to the bed. I wanted to say something, anything to ease the tension but my mind was blank.