Mike, my new boyfriend, likes both my sister Alexandria and me, and when I was away last year he dated Alex a couple of times, although purely platonically. Alex was always quieter than me and never had as many boy friends, so she often came with us to the movies, or out on a picnic, or to parties.
Then on New Years eve last year Mike and I decided to hold a party at our house. It was very successful, and a lot of people turned up. Alex met a nice guy and was dancing with him most of the evening, but when it was all over, I found her by herself in the bathroom in floods of tears. They'd had an argument about her going home with him, and he had called her a bitch, and a tease, and it was all pretty unpleasant. Anyway, she cheered up a bit, and Alex helped me tidy up the place, then Mike and I went to bed, and Alex was going to sleep on the couch.
But about halfway through the night, Alex came into our bedroom and got into bed next to me, and was still very upset. I cuddled her, and we went to sleep. The next thing I know, Mike was moaning in his sleep. I opened my eyes, and Alex was snuggled up next to him, gently rubbing his cock. I felt shocked at first, but then I thought - well, she's my sister, I know her well enough.
So I whispered to her, "Let's wake him up and give him a surprise." So I called in his ear, and he woke up. He looked at me, then he looked at Alex, and he felt a hand on his cock, and didn't know whose it was, and he just said quietly, "Oh boy." The situation turned all three of us on. I started kissing Mike and Alex went down on him and sucked his cock. Then I climbed on top of him, and Alex pushed his cock inside me, and I could feel it all wet with her saliva.
I was going up and down on Mike's cock while Alex kissed and fondled his ass and balls, and then we changed places and Alex mounted him, I has holding his balls and could feel them shudder when he came into my sister. Alex came at the same time.
Afterwards, Mike and Alex stroked and licked me until I came off as well, and then the three of us just put our arms round each other and went to sleep.
In the morning, Alex was gone. I think that was the best way. I don't know how we would have felt that first time in the cold light of dawn.
Since then we have had sex with Mike as a threesome, almost every week. Alex just shows up after we are in bed and lets herself in the front door with her key. I think that the relationship has been a great turn on for us all.
