
Probably because the MC doesn't want a vagina and his secret to be found out and to be harrassed at school and outside of it so he's playing it safe. And the brother because this fuckass ML is blackmailing him saying he will reveal the fact that the brother has a crush on the dad. And honestly the dad is probably the type to believe his precious son on a lot of things that's why he's such a spoiled little shit so the brother knows this and can't risk his secret being out. This creepy ahh ML has a lot of dirt on this dudes and he's also not afraid to do whatever he wants so it makes it very hard to deal with him
"But you're gonna have to do exactly as I say from now on..." Ok but why tho. Especially with that other brother being on his side, like . . . Why is he just taking it