My mom feels sick over my brother being gay.

He's being acting up and not wanting to go to school and being showing signs that he's depressed now my mom has gone through his phone and found out he has a boyfriend and he's gay bare in mind he's 12 ... My mom isn't homophobic but she says she feels sick and doesn't know how to talk to him about it and wants me to talk to him and get answers I'm 20 btw I think I'm much more accepting of people being gay but how am I meant to talk to my brother and make him feel safe enough to talk to me about it ?? My mom's also scared if his dad finds out he will flip out because he is very homephobic and uses slurs alottt! I just feel so bad for my little brother I love him alot and don't want him to feel alone in this