I did coke and mdma for several years. Lots of other stuff too. I was and still am pretty darn smart. I've maintained a high paying, professional leadership career. I've been successful by many measures.
I've also suffered with addiction for decades.
Thankfully it didn't ruin me.... But I wonder how much more my life would have been
It's different for everyone of course. But the common factor is that unless and until the individual comes to accept that he or she wants to be free from addiction... There's really nothing to be done about it.
Have you talked to your brother about this deeply and with loving concern?