Dim and George are initially members of Alex's gang. Dim is your stereotypical strong-but-dumb thug (dude's name is "Dim," after all) but he has a problem with Alex's authority. Georgie is smarter and more ambitious—he leads the rebellion against Alex for the sake of financial gain.
Both are traitors to Alex: Dim incapacitates Alex at the Manse site, leading to his arrest, and ultimately becomes a police officer, thanks to the program introduced by the Minister of the Interior. In this position, he gets even with Alex. Georgie dies in a later raid.