I first saw Kelly in a bar and I knew immediately that I wanted her. She was gorgeous. She looked like an Amazonian goddess. Tall, well built, solid looking and generally gorgeous. I was under her spell from that moment on. She seemed to know. Perhaps it was my stare. Anyway she told me that I could go out with her and go and get my chariot as she needed to go home. It was a cold and wet day so I was happy to be invited to take her home. Once we arrived at her home, a rather splendid three bed town house, she allowed me to kiss her before she went inside. The following evening she allowed me to take her to the cinema and there I had my first feel of her gorgeous body. Her tits were everything I could have wished for and in the gloomy light she allowed me access to them. After the film, which I can remember nothing about she told me that I could take her somewhere quiet. I stopped my chariot in a quiet country lane pull in that I had frequented before. Once in the back seats the magic began. I sucked and fucked her for what felt like an eternity. Well until 02:30 at least. Then she wanted me to take her home. At the door I was afforded a nice kiss and in she went. I went home the happiest man in the world. At twenty five I didn't think it got any better than that. I was in love with my twenty two year old goddess. It became a regular thing that I would collect Kelly and take her out, and then onto our spot for great sex, and then finally home again. Not once was I invited in. At first I didn't care as my life seemed wonderful. I was seen out with my gorgeous girlfriend and then had great sex and then none of the daily hassles. But curiosity started to set in. I still knew little to nothing about her other than she was twenty two and her birthday was in February. I knew nothing of her parents or siblings, if there were any, or other extended family. When I asked her anything she was always quick to change the subject. I started to wonder if she was embarrassed by them or ashamed of them for some reason. Perhaps her father was a mad axe murderer or worse. I started to arrive earlier and earlier to see if I could see someone coming in or out the house. Then one evening I caught Kelly getting home in her work clothes and scooped her up and whisked her away to a country pub. She seemed a little taken aback. She was dressed in a nice blue skirt suit and a tight white blouse that emphasized her gorgeous tits and her long hair was done up in a bun. She looked like a power secretary or a school ma'am or solicitor. I quizzed her about her job, but just as before she was quite evasive. Later at our spot I discovered that she wasn't wearing anything under her skirt. That made me extra excited although it did make me think about who else was she panty-less for. The following evening Kelly didn't seem her happy self and although we had a good time and another great fuck at our spot, there seemed something not quite right. It worried me. Had I got her pregnant. We had never used condoms and like all my questions I never got an answer about contraception. I thought that she would tell me in her own time if I was to be a father. I even got a tingle thinking i might be a dad. The following evening all seemed fine again and was like that for another few days before she seemed off again. I couldn't put my finger on it. Or perhaps I had and that was the trouble. Then one evening Kelly told me that as I keep asking questions about her family I would be meeting them for Sunday tea and to wear something nice, a suit preferably. I didn't own one so the following morning I skipped work and went and bought a suit and some nice shirts a tie and some shoes. I wanted to make a good impression, especially if Kelly was going to make an announcement of our baby to be. I was sure all the upset was because I had got her pregnant, not that anything showed yet. On arrival I was met by Kelly at the door who announced that they were all in the garden. I took all to mean siblings as well as her parents. I was led through a beautiful looking home and out into a very large garden. Sat around two very large tables were quite a lot of people. I was first introduced to her parents. Her mother Joyce was like Kelly Tall and well built, an older model but still very attractive. Her father was shorter and stocky and had an air of money about him. Then there was Sondra. I was stopped in my tracks. She was an identical twin to Kelly. My thought was the baby would change them from being identical. Then her brother, aunts and uncles and Tommy. I wasn't sure what the connection to Tommy was. Anyway the tea party began and caterers were bringing around food and drinks. I was waiting for Kelly to make her announcement, but it never came. I wasn't sure if I should be grateful that she was keeping it for another time and not ruining what was a family get together. By the end of the afternoon I still hadn't learnt much more about Kelly other than she was a twin and she had a brother and aunts and uncles and then there was Tommy. The next evening Kelly was quite bubbly and started to open up about her family. I wasn't wrong about her father he was a multi millionaire who did something in the city. I could see some resentment when I asked about Sondra and all I got was that she was the older twin and whatever she wanted she generally got. There was a small hint that it generally included boyfriends. There was no problem there as I was more than happy with Kelly. I told her that her brother seemed nice. Then I asked her what was Tommy's relationship to the family as I hadn't caught that. Kelly went quiet for a few moments and then blurted out that he was her fathers partner in business and also her mother's lover. I nearly fell off my chair and choked on the mouthful of beer I had taken. I had to ask, "Did you say he was your mother's lover. Kelly said, "yes" and there was worse to come, "And he is mine and Sondra's father." She went on to say that her brother was her fathers offspring and not Tommy's. No wonder she was keeping her family to herself. She continued and told me that Tommy lived with them and her mother split her time between her father and Tommy. It put any problems like Kelly's pregnancy in the shade so to speak, and what of her pregnancy. I had to ask. Kelly put me straight that there was no pregnancy and never had been. She wondered where I got the notion from and I said it was due to her strange moods. Kelly's face went red. Had I just put my foot in it. Kelly went quiet and when we went to our spot she didn't put her normal effort into our love making. On my drive home from her house I tried to analyze everything I knew. First her mother, who was beautiful by the way, had a live in lover. Her father wasn't her father. She was a twin and a brother and she wasn't pregnant. I couldn't do much with the first few things but why had I thought she was pregnant. It was her strange and quiet moods that had triggered my belief. Then it struck me that I had seen Kelly almost every night in the last three month period. That was it she had never had a period. That's why I thought she was pregnant. No periods equals babies. Perhaps it was due to her contraception that she didn't have periods. I didn't have anyone to ask and I certainly wasn't going to talk to my mother about it. Another day off work and I was in the library. I had no idea where to look and was pulling one book after another and the pile on my table was growing when a School Ma'am looking librarian asked me what I was searching for. It was awkward to ask as she was quite sexy, definitely my type, but none the less I blurted out that wanted to read up on contraception. "Good for you, was her reply, "anything specific about contraception?" Some how I ended up telling her that I wanted to know if there were any types that stopped periods altogether. She thought for several minutes and then went off and brought back two very large books and then removed my growing pile. After a while she returned and asked had I found an answer. I told her yes and no. She sat down next to me and I told her there appeared to me medical reasons why some women don't have periods but most of those resulted from surgery and Kelly didn't have any scars. I got a sideways glance from her when I told her that. If I wasn't with Kelly I would have chatted her up as it was such a sexy look. Anyway I continued to tell her that I couldn't find any contraception that fully stopped periods. She told me that she had not heard of any that did either. That left me with a problem, why wasn't Kelly having periods if she wasn't pregnant. I had to know even if it upset Kelly when I asked. It did, but I got my answer. When Kelly was having her periods her sister Sondra was stepping in and taking her place. My god I had fucked my girlfriends sister and didn't know it! The upset was that Sondra wanted me and was used to getting her way, and after she had, she would discard me when she got bored with me. I told Kelly I wouldn't let that happen as I was in love with her and not Sondra. I asked what her parents would think about that. Kelly told me that it had happened before and they didn't seem to care. They were too involved in their own strange relationship to bother getting involved in squabbles between the twins as Kelly put it. It took a few days for me to get used to what was happening and to put a plan together. I agreed a password with Kelly so that I always knew when I was with her and not Sondra. The first time I knew I was with Sondra I got her to the quiet spot as quickly as I could. Once in the back seats and Sondra undressed I was on her with my trousers around my knees pounding her for all I was worth. Then in full flow I stopped, pulled out and asked her, "Did you bring some KY jelly with you?" Sondra looked confused. I continued, "Just as well that I brought some," and pulled a sachet from my trousers that were around my knees. "Why do we need that," Sondra asked in an almost squeaky voice fearing the answer. "You promised me that tonight you will let me have your arse," I told her. "Have my arse, she repeated. "Yes your going to let me fuck your arse hole. That's what you agreed. Now just roll over so that I can rub some in so my cock will slip in easier," I added. "No, I didn't agree to that," she squealed. I told her that she had. "No, No it wasn't me it was Kelly that must have agreed," she finally confessed. With that I threw her and her clothes out the car and jumped into the front and drove off leaving her getting dressed. I gathered from Kelly it took her nearly two hours to walk home. After that Kelly and I had no further interference from Sondra, although their mother was another story.