She had pretty much grown up at my house.  My wife's little sister was like my own little sister.  As she got older we flirted innocently until she stayed over one night. Around 2 am one night, I went to the bathroom and bumped in to her in the hallway. She was just wearing a tank top and her panties and looked so hot.  She teased me about how everyone else was fast asleep and that nobody knew that we were both out of bed. She said "it is a shame that we are related and started to walk away". I came up behind her and grabbed her and pulled her close to me to hug her from behind, that is when she pushed her ass back in to me.  I kissed her neck from behind and reached down to touch her. I caressed her tummy hand my other hand on her side.  My hand slid up under her breast. She took my hand and moved it up so that I was cupping her tits. with my other hand I slid it down and reached in to her panties.  My hand found her pussy incredibly wet, so I slid my fingers inside of her.  She started to groan and spread her legs wide.  I continued to finger her as I rubbed her tits. It wasn't long before I felt her start to cum.  Her whole body convulsed as wave after wave of pleasure tore through her body. When she was done, I stepped back as she turned around I said "you are right, if we weren't related, I would have fucked you right here". I turned away and walked down the hall and left her standing there with a dripping wet pussy thinking about fucking me in the hall.