Hi, I'd like to help you with your question.
I'm sorry to hear about your brother's situation. Depression can take a toll not only on the person, but the family as well.
There are many ways to help your brother. But first, determine if he wants your help. If he is refusing to let anyone help him, it will be very difficult to do anything for him. If he is willing to accept your help, then you can start by telling him that you are there for him. Let him know he is not alone. You can do this even if he refuses your help.
Also, become acquainted with his treatment. What medicines is he taking, is he in individual therapy, group or other type of therapy, what other treatments has he had. These are all important to know so you can help him find the best treatment options and therapists.
You can also attend his psychiatric appointments so you can help your brother ask questions and remember information the doctor tells him. You can help him to keep track of medicines, side effects and follow up appointments.
There is an organization called NAMI, the National Alliance on Mental Illness that can help you find local groups and resources to help you, your family and your brother. The are at http://www.nami.org/.
There are books that can help you as well. One is called Undoing Depression: What Therapy Doesn't Teach You and Medication Can't Give You by Richard O'Connor. Also,
Talking to Depression: Simple Ways To Connect When Someone In Your Life Is Depressed by Claudia J. Strauss and Martha Manning. These are good resources to help give you a start with helping your brother.
I hope this has helped,