My friend at work, Harry, had been trying to become a father for some time. His lovely young wife (22) was keen to start a family. He told me his wife Sara, feeling they were putting too much pressure on each other, decided to go back on the pill, and that they should try just to enjoy sex again. He had told me once before that he fantasised about her being fucked by another guy. He brought this up again, and suggested he would like me to join them for a threesome. He had been to the gym with me and noticed I was well endowed, 8 and a ahlf inches, very thick, big bell-end. He had told his wife one night when she was tipsy and she had said she would not mind being fucked by me. He had followed this up and she said she was agreeable. So what did I think? The only condition was I was not to come inside her. Now Sara is a lush, pert shapely young woman. How could I resist? A night was agreed and I went round to their place. After some drinks Sara suggested we watch some porn. She was dressed in a very tight dress and was looking very tasty. Harrry had noticed how entranced I was by her. We watched some steamy group sex, and Sara, sitting beside Harry, began to rub his crotch. Soon they were kissing passionately, and I was feeling a bit of a gooseberry. However, Sara then moved over to my chair. She sat on the arm and said, "Harry tells me you are a bit of a stud, can I see if what he says is true?" I said "No problem", and she began to unzip my jeans. I was already quite hard. She reached in and gasped as she grabbed my cock, releasing it from my jeans. "My God, that's huge!" Even Harry was staring in astonishment, never having seen me erect. She began wanking me slowly. Harry came over to beside the chair, undid his trousers and released his 5 inch cock, pushing his wife's head towards it. She began sucking him like an expert. After a few minutes wanking me and sucking Harry, he suggested we go upstairs to the bedroom. Soon we were all naked and with Sara between us, we were soon licking and sucking her tits and cunt. Sara then surprised us by saying she wanted both of us in her pussy at once. Harry lay on his back and Sara mounted his throbbing cock. She the told me to take her from behind and to push my cock in beside his. This took me several attempts but she groaned loudly when I finally managed to manoevre it in. Harry began humping his wife and it was quite an erotic feeling having another man's cock running up and down my length. I then began a fucking motion of my own and we soon got into rythym. She was gasping and moaning and this spurred us on. After about 5 minutes I heard Harry grunt and I could feel a wet warmth in her cunt. He had shot his load, but I was some way off. His softening cock slipped out, and I was left with a clear cunt to plough. She raised her arse like a cat in heat. I picked up my pace and Sara was now making a lot of noise, screaming fuck me you beast. She climaxed twice during the next 10 minutes. Harry was pinned beneath her but she seemed unaware of his presence as she lost herself to my now hard thrusts. "My God your cock is reaching me in places Harry has never managed. Give me your seed, come in me!" Harry started to say "No Sara" but it was too late. I had gone past the point of no return. I unleashed my load deep inside her. I am a very heavy cummer, so there were about 10 large spurts. She screamed "I can feel it" as she came again. We collapsed on top of harry, then I withdrew my cock. Come flooded out over harry's limp dick. She kissed me, muttering thank you, thank you. We had another drink and Harry wanted to fuck her. He got on top of her and she sucked me hard as he did so. His eyes were nearly popping out as she deep-throated me. This brought him over the edge and he pumped his come into his wife's cunt, already soaked by my heavy load. I then came in his wife's mouth, so much it was dribbling on to her tits. The week after this I was seconded to the States for a year. When I came back Harry showed me pictures of his new daughter, a lovely little girl. When I asked about when she was born I realised with horror that this was my daughter. Sara had tricked Harry over being on the pill. He had convinced himself that he was the father as they had fucked furiously for a few nights after I had been there. She had been frenzied in her demand for sex. He said it was the experience with me which had made her want fucked so much. Although he said he was a bit put out when she described in detail how she felt as I was fucking her compared to him. She had to ask him if he had come in her, and told him she could feel the come jetting out of me. Three months later I bumped into Sara after a works' night out. She told me she had not had an orgasm with Harry since that night, only coming masturbating when thinking of my rampant cock deep inside her. She begged me to fuck her again. We booked into a hotel and I fucked her for all I was worth. She was insatiable, and I must have filled her with come three or four times. Now she is pregnant again, and Harry is delighted. I have told Sara that I enjoy fucking her but next time I am going to use a condom. She promised to be on the pill because she loves the feeling of my bell-end spurting come in her. Can I trust her? Can I resist her? She is a supreme little slut bucket!