I want to f*** my gf's dad.

My girlfriend is amazing she's 18 and i'm 17. she has THE best body and is great in the bedroom. BUT. i want her dad so bad? i don't know why?! i saw his d*** in a photo of him and my gf in the bath when she was about 2 and it was pretty huge! ever since then, i've thought he was the hottest man alive. he's not a fat wrinkly dude... he's well built, young looking with a six pack and... a big d***! is this wrong? should i make a move?