My son introduced me to his girlfriend. She was gorgeous and I wondered what she was doing with Alan, she was far to classy looking for him. Over the next few months I got to see a fair bit of them. It turned out that Alexis or as Lexi as she was commonly called had no family as she had been fostered and had fallen out with the foster family. She had moved in with Alan and when she called around would call me dad. I liked her, she was hot, and she knew it. My son, the dope would often argue with her and it wasn't long before she was coming to me in tears. I would comfort her and the next day she would go back to Alan and make up with him. I had lost my wife shortly after Alan was born and had raised him on my own. I had been with a few women since my wife passed and had a couple I saw fairly regularly, she needed sex and he wasn't able to supply it and I was his stand in. A good arrangement for us all. It was getting late and there was a knock on the door. There stood Lexi in tears. Another argument, but this seemed worse than normal. After she settled down in bed I locked up and slid into my bed. I was just dozing when I felt someone getting into bed with me. For a second I was thinking of Rhona, my regular lover, then it hit me. It wasn't Rhona, but Lexi in bed with me. It was too late my cock was already rock hard. Lexi snuggled up to me, and as I never wear PJ's, it was skin against skin. All she had on was a bra and small panties. There was no hiding my hard on and Lexi immediately discovered it. She gave a little squeal as she grabbed hold of it. I wasn't sure was she upset with me or what, after all she was in my bed. I soon found out as she rubbed my cock up and down the crutch of her panties. If it were possible I got even harder. Then her tongue was in my mouth as she continued to rub my cock. Well I am a red blooded man, so I soon had her bra off and her tit against my chest. They were a nice size, big enough for a good handful but not so much that there was a lot of waste. She was still kissing me as I started to stroke her arse. It was nearly three weeks since I had seen Rhona last, and was more than ready for sex. Lexi pulled away and removed her own panties. Then she was back rubbing my cock up and down her slit as she started to kiss me again. I had my hands on one tit and the other on her arse. I pulled her to me. I'm not sure if it was just good timing or Lexi engineered it, but my cock instead of sliding up her crack, sunk deep into it. It was good, in fact very good and the tightest pussy I had been in for many years. We fucked in this position, facing each other for quite a while before I came in her pussy. Then we just lay cuddling and breathing heavily. I woke and it was still dark and I could feel the warmth coming off Lexi's body and my cock was getting hard again. Lexi's back was towards me and I slipped an arm around her and cupped one of her tits. She let out a soft moan and shuffled backwards against me. My cock was against her arse and It felt good ad as se wriggled against me I also wriggled down just a little and my cock slipped between her legs and nuzzled against her pussy. Lexi groaned and wriggled a little more and my cock slipped right on in. It was another delicious fuck that resulted in mutual climaxes and me coming in her again. We woke as the sun ripped through the crack in the curtains and we fuck long and hard a third time. I couldn't believe my luck that this gorgeous young lady was happy for me to fuck her. Then the doorbell rang. I was quick slipping some clothes on and going to the door. It was Alan and he had come for Lexi. I was worried stiff that he would go upstairs and catch her still in my bed. He breezed past me and up the stairs. Was I relieved that Lexi had heard him and gone back to the spare room. They talked for some while and then she dressed and left with him. It seemed that every few months they would argue and she would end up at my house and in my bed. Then they announced that they were getting married. It was a very quiet affair. Just four of their friends and myself attended along with the happy couple. It was just after the honeymoon that they had another argument and Lexi again ended up in my bed. It was one good fuck and we had just come out of the shower when Alan came and got her. Another close miss! Then four weeks later they inform me that Lexi was pregnant. Over the next eight months Lexi spent several nights at my house and we fucked like rabbits. Alan was not keen to fuck her as she got bigger. I on the other hand enjoy pregnant women. I think they look, feel and smell great as the get ready to give birth. She had a boy and seemed to be a great mom. He was almost six months when they had their next argument and she turned up with her son. We again fucked like rabbits and again in the morning she went home with Alan. The lad was just over a year and walking and talking when again she turned up. After getting him settled. We were at each other for several hours before she went and slept with him. Six weeks later they again tell me that she is pregnant. They seemed over the moon. Again during the pregnancy she ended up with me and in the sack. It was a girl and Lexi still continued to come to me for sex. Then she was pregnant again and all through the pregnancy she found times to get with me. After her second son was born, Alan announced that he was going for the snip. After that I had to get in a supply of condoms. It was almost three years when she told me that she was pregnant again and that she hadn't told Alan as he would obviously know it wasn't his. I asked what she wanted to do and she said even if it meant loosing Alan she wanted the baby. I assumed the baby would be mine. She asked would I support them if he kicked her out. I told her I would. The following night she was back in my bed after she had an argument with Alan, probably over the pregnancy. He again took her home the next morning. They patched things up and Alan said he would bring the baby up as his. Again during the pregnancy she continued to slept with me. Another boy. I wondered about the kids and were any or all of them mine. When I could I took DNA samples of each of the kids and sent them along with mine to get them compared. I also sent a sample of my sons, his toothbrush, he thought one of the kids had took it. Then I waited. It was the worst wait of my life and the results were a shock. The first three kids all had the same father. I was their biological father and the last was from an unknown contributor. I had bred her three times. Lexi had obviously played away from home for the fourth, but not with me on that occasion. I never told them that I had done the tests. My son was bringing up four kids and not one was his. I think Lexi knew, but we never discussed it. Then Rhona's husband died. I spent lots of time helping her sort things out, and then the obvious happened, she moved in with me. Lexi wasn't happy as she had now lost me as her sex mate. She still used me as her refuge. She still would end up at my house, but in the spare bed. Now another fifteen years down the line, I married Rhona and Alan and Lexi are still together. No more kids fortunately. My son still doesn't know, as far as I can tell that he has never produced any children or that most of them are mine. He was an excellent father to all four kids and still supports them to this day. I did tell my secret to Rhona who thinks it funny that Alan brought up my kids. She would never tell Alan or say anything to Lexi and enjoys all four kids calling her Nan.