Billy the kid and the Lincoln county wars?

The movies Young Guns and Young Guns II have a lot of "Hollywood made" scenes and myths about Billy the kid and the Lincoln county wars, However, they do contain many true facts about them as well. My question is, In the movie young Guns II, Tom O'folliard was portrayed as a 14 year old boy who wanted to join up with what was left of the regulators after Billy took charge. Was Tom O'folliard really this young? Or was this another hollywood glam moment?