The fact that you mentioned that you are concerned by the way he acts leads me to believe that your brother is going through some sort of mental anguish or pain. He may need more attention than you are capable of extending. I would suggest he be introduced to a councellor who may be able to identify his disability and take positive steps to rectifying the situation.
Yes, it's important to know whatś wrong. Physically, mentally, in between the wrong people?
When it is the last, there is little hope, I know for a sad fact. ;-( xW
You did not say whats wrong with him.