A "good bro" is a colloquial term for someone within the anabolic/androgenic steroid community who is generally reliable and helpful.
Hey Bobby, did you see that massive dude? I bet he's a good bro too!
Someone who represent's all things good. The type of person you want to surround yourself with.
Lestat is a good bro. That's good bro material! superqt loves good bros. Radar is king of the bad bros.