His girlfriend catches him doing dirty things with his sister
Being in the same house with his sister-in-law has been a problem for him. But one of those problems that has a solution and that is not going to get any worse. Basically, he just lets himself go because when you’re with slutty girls, you have to let them take control. Later, his girlfriend catches him doing dirty things with her sister and the pervert stares. It turns him on so much that then she wants to eat his cock and feel it inside her pussy. Because that makes her very horny and those are the things that a man should take advantage of while he is young. Which is when those things happen.