Help

So I just remember about a yaoi manga I read a long time ago, it was about a two step brothers I think and the oldest one look younger when the younger looked older (the oldest one had black hair and the the other one had brown I think or blond ) well one time the youngest one goes to to sex place and there there ar a room where you can pay to fuck and ass ,all you can see is the ass and the butt is just sticking out so he fucks it and than I don't know how he realizes that his brother is working there and he confronts him about it when they get home, please help