Hey Joe,
The other Joe, above, said a lot of the things I would say. I think it’s really really important to remember that your brother is 16. When my brother was 16, he was NOTHING LIKE he is today – he was an atheist, he was sexually all over the place, and he rebelled against everyone and everything. Today my brother is a peaceful Catholic with a wonderful family. People change. Our pushing hard against them can sometimes give them reason not to change, though.
He cares about you. He’s not crazy to be worried about how you will make it, as a guy with SSA in this culture, without getting a husband. Jesus is the life for you, but His Church is still working out the details about how to pastorally approach people like you and me. If your brother looks at individual Catholics and sees lots of things that are not loving to you, I think he may be seeing some of these things correctly – you don’t “lose” if you admit that. (For instance, I’ve heard some Catholics say that people with exclusive SSA can never be allowed to live with anyone else except their family, for fear of “near occasion of sin”. That sort of statement doesn’t demonstrate genuine love, at all, IMO).
Perhaps the best way to push back gently is simply to suggest that his views do not come from some Fount of Reason, but rather from a different sort of brainwashing.
To the question of whether he will come around, again, he’s 16. What he does in the future is anyone’s guess, but you two have a LOOOOOONG future, and the temptation is to put too much stress on the situation now. You’ll have to be patient with each other, and you can set the tone for that, Joe. Patience is perhaps the most characteristic aspect of God’s love for us, and it needs to be central in our love for one another, too.