Here's the way to approach the problem. You should talk to him nicely, saying that you realize he took the money but let him know that you don't blame him. But you must let him know that doing such things behind your back is not nice, if he really need money, he can ask from you. Because if you have money, you can help him. But if you really no money, then you want to help him financially also cannot lah. You MUST tell him, because the problem isn't stealing from you, the problem is when he steals from others, and he can go to jail for such things. You may give him a second chance, others may NOT! Secondly, what I would do as you, is to hide and lock away the wallet/valuables and prevent such things from happening again. Trust me, talking to him nicely and showing him you care for him despite what you realize, is going to build a stronger relationship and also to put him into the position for him to clear his mind and go the right path.
What is your relationship with your brother? All good besides this issue?
Well stealing is definitely wrong, everyone knows that. I think you should just catch him in the act and ask (nicely and calmly) why he is doing this.
Don't assume he's doing it cause he's a thief or what, for all we know he has deep financial troubles he has yet to reveal to you or your family.
Yer can't even talk to yer bro regarding the stolen money, means u r
1) Not so close
2) Scared of him'
3) Easily manipulated by him
If u can't even deal wif him regarding wallet, next time when u all big and married, he is going to take yer parents property deeds n money for himself. Learn to stand up to yer brother. It is unacceptable for him to take yer wallet in front of yer face. How would u feel like if I do the same to u? Of cuz u want to whack me. Same thing here for yer brother. Wallet is very personal thing. If u allow him to take yer wallet, its like he taking yer diary n reading all yer private stuff.