My sister came to my place and asked me if she could spend the night 'cos she didn't want to go to our parents home. When she arrived I was drinking and watching porn with a friend and the first thing that came to mind mind was "Ok, if get undressed and let me fuck you, I let you stay for the night.". The problem was I not only thought it but I said it. For my surprise she accepted, started to undress and we did it on the floor.