This is fiction!
My Sister-in Law (Debbie) is now on her own, her husband left her for the usual younger, slimmer woman and she has been devastated by the experience. My wife (Julie) and Debbie are very close and we have been spending a lot of time with her to help her get over the bad experience and give her back some of her self-esteem and confidence.
A few weeks back she was over at our house for dinner, she doesn't normally drink as she drives but on this occasion she was staying over as the girls were going out the following morning so it all made sense.
Over dinner we were on our fourth bottle of wine so the conversation flowed fairly easily and inhibitions were relaxed shall we say.
I asked Debbie what she was doing for sex now that she had been on her own for a few months, she coyly replied that she'd resorted to a fingers in approach which made us all laugh.
She went on to say that she was jealous of our relationship and that she'd do anything to be part of a relationship like ours.
What Julie said next made my cock twitch and sit up straight, she said to Debbie "Well ask if you want to be part of our relationship, we have a king-size bed so there's plenty of room".
The room went very quiet and we sipped at our wine, eventually Debbie looked at me, then at Julie and said "Well if that's an invitation then I'd like to take you up on it."
At this I stood up and stood behind Julie, my arms over her shoulders so I could fondle her large tits, looked at Debbie and said "You'd be very welcome but things will only happen if we are a threesome."
With that I undid the buttons on Julies top and exposed her tits to the room, rolling her large erect nipples between my fingers, pulling them out, stretching them and making them harder than they were already.
Debbie had even bigger tits and she undid her top and started to rub her own nipples, she came and sat next to Julie and I reached over and started to play with her tits, one hand on each of the sisters' tits, I was in heaven.
Julie reached behind her and grabbed my cock which was harder than it had been for a very long time, she gave it a squeeze and suggested we retired to the bedroom.