Dad Screwing Sisters Friend

My younger sisters mate amanda who is 15 comes round all the time i didn't think it was for any other reason than seeing my sister amanda is skinny around 4'7 with shoulder length blonde hair and with what guys would call blowjob lips and the one thing guys notice first is her big tits my mum and sister was out leaving my dad at home by himself i came home as i walked towards our kitchen i could see my dad who had his back to me talking i thought he was talking on the phone then heard the words you're so beautiful and a pair of legs appeared either side of him and caught a glimpse of who it was it was amanda laying back on our kitchen table completely naked and my dad pulled down his shorts and stepped forward and heard amanda moan out so loud and my dad grunting and he started to screw her by now i could see her tits going back and forth he was giving her everything so many times i heard him say she was fucking tight i was in shock with what i was seeing it only lasted 5 minutes and his legs buckled and knew he was ejaculating once he stepped away she carried on laying back with everything on show i don't think it was the first time either.