I have nothing to offer you other than my full sympathy for you and your troubles. I know virtually nothing about post traumatic stress and I never had to deal with it in person. I do understand that it can be excrutiatingly hard to deal with... I certainly have no advice for you; however I can offer you my full wishes of strength and courage to deal with this situatiation and hope that what your brother - and, in fact, all your family - is going through is nothing but a hard phase of his life.
Some good advice has come up in this thread and they are given by people that are indeed more experienced than myself, be it because they are older, because they served in the armed forces or because they know better than myself. I wish you all the best. Good luck.