My wifes sister came to stay. Hello this story took place in the 1970`s my wifes sister stayed with us for 2 weeks while her place was being decorated.My wife was 21 years old five foot two inches size ten dark brown hair,Her sister jackie was 18years old the same size but slitely bigger boobs.My wife loves me giving her oral and I love doing It,it is a big part of our sex life.I am the only man she has had sex with unlike her sister jackie who has had a more active sex life.My wife told me that her sister also liked receiving oral sex although her present partner did not like doing it.On the second night jackie asked my wife if she wanted to go out for drink with her I said I didn`t mind so they got ready and off they went.They came home at just after two am,I was laying in bed when she came into the bedroom,she got undressed and got onto the bed she was a bit tipsy, she asked if I would give her oral as she felt horny, I didn`t need to be asked twice and down I went she was very wet and her clit was bigger than usual she pushed her pussy hard into my face with my tongue pushed inside as far as I could get It after about 15 mins she orgasmed .After a few mins she moved down and started riding me with her tight pussy.In the darkness of the room I heard movement then I felt the bed move on one side then all of a sudden I had a pair of legs stradle my face and a very wet wide open pussy press hard down on my mouth I pushed my tongue in and a blob of spermy liquid ran into my mouth .My tongue went to work and I soon had her orgasming then as quik as she apeared she was gone I shot inside my wife and she rolled off and we both went to sleep.The next morning my wife was up when awoke I went down to the kitchen where my wife was sitting having a coffee she looked a bit worried,I sat down and said what was that all about last night and she said she was sorry but she got so turned on with what happened when they went out, that she couldn`t help herself. I asked her did It not bother her that her sister had come into our room and sat on my face, she then told me that they had planned it because her sister needed oral as she had not had it for a long time and she thought that I would enjoy it.I told her that I did enjoy it but that her sister had far bigger pussy than her tight little one and that it tasted like she had had sex as there was salty spermy taste!that is because she did have sex with her boyfriend and It was the fact that my wife watched her that had turned her on so much.I asked her why it was so exiting watching her sister have sex, she said because jackies boyfriend had a rather large cock, how large I asked ? 10 inches long by 2 1/2 across she said {that explained why her jackies pussy was so large}.My wife went on to tell me that he was also a heavy cummer and that I was lucky that I didn`t have her over my mouth straight after getting fucked. I had to get to work so I said we can continue this talk tonight.