I don't know who's RJ, but it's definitely not Bret Partridge. Everyone who thinks it is him is taking all the clues too literally. You can't trust anything of the details about height, weight, beard, hair, age, etc. since they change over time and could easily be frauded. 

Even if Red John is a group, there is still a leader to that group who is the true RJ. The 7 people list could be a white lie on the producer's part on so many levels. Maybe someone on the list is technically a RJ, but no the leader. Maybe Jane had more suspects and lied to Lisbon. 

Anyone arguing for PJ is also wrong. Multiple personality disorders do not work like that. There's no way he could keep a part of his personality away from himself and everyone else. Obviously the childhood memory is extracted from a relative of Jane's; there's no mindreading or hypnosis involved for that either.