Lou, the blue-collar, less-ambitious brother of Sal, is a garbage man's apprentice when the film opens. If Angie is Sal's right-hand gal, Lou is his left-hand man, helping him launder money from less-than-legal dealings by holding one of Sal's car titles in his own name. He's the main man on the ground, biding for the right car at the police auction, and organizing the New York troops to help carry out this big-money deal.
As Lou and Sal hug joyfully, after what they believe is a successful trade-off with Charnier, it's hard not feel a little choked up. Sure, these are criminals, but they're also family, and as viewers, we're well aware of how doomed they are.