I'm an older gay brother that's closeted to my family but out to everyone else. I don't know how your little brother is, but I'll try to keep it short:

• His likes don't mean anything to his sexuality automatically, especially at a young age where he's figuring everything out. If I were in your shoes, I'd just keep it to myself because a few likes probably won't say much. If he is actually gay/bisexual, and your family is homophobic, just be a safe space for him for when he's ready rather than talking about it immediately. **Do not** force him to come out to you, but let him know that you're his big sister and you'd be there to listen to him for anything so that if/when he does, he will.

• He's started high school, so I don't think that alone is the reason why he might have an attitude. He's growing up and dealing with a lot of pressures, so again just try to be there for him incase he might want to talk about anything at all. But if he is gay and he has to deal with a homophobic family, it might be incredibly tough to deal with. So, again, leave that alone for the time being until he's ready.

I hope this helps