I was travelling around for skiing a few years ago and my girlfriend (now wife) asked her sister if i could stay with her for a few days because she lived only 20 minutes from one of the mountains. Her sister lived in a studio apartment so we would have to share a bed. My girlfriend had no problem with this because "its not like youre going to hook up with my sister", and i didnt, on the first night that is. The second night however she came in from being out at the club and she was pretty drunk. She nearly fell over as she stripped down to her bra and panties and climbed in bed next to me. Without saying a word i just went down and moved her panties over and started eating her pussy. I knew she would be too drunk to care and would just go along with it. I ended up coming inside her

I told my girlfriend about it because i wanted to be the one to tell her. I was very surprised when she wasnt mad. I guess she kind of fantasized about something like that happening. She told me all about how they would play with each other as kids and how she might find it fun to go visit her soon. So yeah we still see her a few times a year and we have plenty of sex together when we get the chance