Is there any way to become legally able to talk to my brothers doctors?

This may be the only option if he is no longer competent. If family members decline to pursue guardianship, which they can, the court may assign someone else as guardian.

To my knowledge, there is no restriction on what you may say to his doctor. Without proper consent, he may not provide you with information, but I would certainly give the doctor info if you think it is helpful. I wrote a letter to my cousin's doctor and she reviewed it before we met for the appointment.

I'm confused, because doesn't his doctor already know that he has TBI? If his behavior is concerning or he is having more medical problems, I would let his doctor know immediately.

Is he still able to appoint a Healthcare Power of Attorney and Durable POA? With his condition, he really needs to do that, though, from what you say, it may be too late. If no one is appointed and he is not able to make his own decisions, the doctor, neighbor or some one in the community could report it and the court may appoint a Guardian. Or you may Petition the court and ask that they appoint someone else if you and your sister do not feel as if you can do it. Do you think that he is competent to take care of his household and make sound financial and medical decisions?

I wouldn't wait until there is a crisis to make the arrangements. Is he able to understand what you are trying to do for him and why you are concerned or is it beyond that point?

Sorry about the confusion. This describes my mental state for the last few years. His primary Dr. is aware of the TBI diagnosis which was done by a Psychiatrist I believe. He is not forthcoming with information which is why it has made it very difficult to understand his situation. He is capable of living on his own but can't work and his income from the state is far from allowing him to do this. I am aware of programs and opportunities where he can get more help but until we have the ability to discuss things with people we are just running in circles. Talking to him seems affective at first but he doesn't follow through and is a master at procrastination. I very much appreciate your input. Thank you. Any more thoughts are welcome.