Best suggestion I have is get help for the family too. He sounds willing to participate in treatment which is great (and isn't always the case). Perhaps since the family hasn't been exposed to his addiction (or known of it) for a long period of time, they may not be as adversely affected as someone who is tumbling in their addiction while the family struggles to help (often in very unhelpful ways without knowing it).
Consulting with a profession who is well versed with addiction would be a great start for the family. Your brother (assuming he proceeds with OP) will be getting the help he needs but often the family needs guidance to know how to appropriately support him.
Welcome!
gentle hugs
ke