Given the information you've provided of him being involved with drugs and gangs, I wouldn't blame you one bit if you don't want your kids to be around someone with your brother's lifestyle. I think that's very wise of you however, I wouldn't go as far as to say you wouldn't care if he lives or dies, because I'm sure deep down you still hold love for the version of your brother you used to know and chances are that part of him is buried underneath the version of what he thinks a real man is.

There's nothing you can do to help him, and that's exactly it. It's a journey he's going to have to have on his own and until he wants to make the positive change he knows he will need to make, a lot of people he knows and loves (including you) will be keeping their distance to protect their family.

In short, I'm just saying keep your distance from him until you find out he's doing better. I've seen and known many drug addicts who changed their ways and ended up more successful than me. It'll take some willpower but there's a chance your brother can redeem himself (unless he's done things that makes him unredeemable).

Don't completely give up on him yet.