It is hard to accept you can no longer do what you like to do. I wonder if there's a hobby or something else that can distract him and bring some joy. I know for my friend it is to live on her own again instead of in a home for the elderly (nowhere else was room). She had one good day per week and needed help but we could arrange it in some way. She liked reading so I took piles of books for her from the library, things like that.
It must be possible for your brother to do something since many deal with the same he does.
I wish you all the best. I will ask in some time again if it's okay with you