What would you do if your brother did not believe in God?

[Brian]

highfive him.

Ask him how you can achieve rational thought as well?

[Joe S]

I would just ask him what his reasons were. I wouldn't try to change his mind without knowing why he changed his belief system.

[Joe]

i would hope that he would come around. i did, and i'm happy that i took myself away from the title of atheist. if he didn't come around, in time i would have to talk with him, and if he still chooses not to believe, than its his loss.

[storm]

I'd get over it.
It's nothing to do with you! Please don't let this ruin your relationship!
Just don't talk to him about it the pressure of it will but strain on your relationship.
DON'T DO ANYTHING!
He'll be really angry if you tell him what to believe.