How do I make my brother believe again?

u can't really 'make' him believe. Sharing with him some signs that you've received/are yet to receive may encourage him to believe, but I cant assure u that it will work. u can also share with him some experiences others have had with him as well (as long as they're all true). That could also help as well. I cant promyou that your brother will start to believe again, but I wish the best for u :)