Have the doctors made an actual diagnosis yet?
It can make a big difference in treatment whether it is a personality disorder, schizophrenia, a mood disorder, etc. that is being dealt with.
In the meantime, any visits you make, cards you send, calls you make (if possible), mean more than your brother would be able to express right now.
I have cards my sister sent me from 30 YEARS ago - the cards, and what they meant to me back then are as fresh as yesterday...