It's been awhile since I've seen the movie, and I just know I'm gonna get details mixed up with Snatch, another movie of the same genre.
Spoiled below for basic plot details.
Thinking about it, I suspect:
4 in each crew: Dog's, Eddy's, Rory's, and Harry's.
Nick The Greek would have been an indy, but it looks like they aren't in the game as a character.
Eddy's Dad (Sting) could be an indy, or might be involved with Eddie's gang somehow.
Harry's hired goons (Gary and Dean) could be another faction.
Eddy's Crew: Eddy, Tom, Soap and Bacon.
Harry's Crew: Harry, Barry The Baptist, Big Chris, Little Chris
Dog's Crew: Dog, don't know the names.
Rory's Crew: Rory, Bunch of stoners, don't know the names.
All factions could have a NK, but Harry's almost certainly does. Infina, why do you think Harry wouldn't have a NK? They would be the most obvious, as Harry's crew would have Barry the Baptist, Big Chris and Little Chris.
Gotta go, thats all for now.