I cant get any companions to follow me (accept dogmeat's puppy).

Over the course of my game I have hired Charon, Cross, Fawkes, and Dogmeat. I just beat the regular portion of the game, in which I had dogmeat's puppy who died, and started the broken steel portion on PC. I have visited all of the followers I have employed and tried to get them to follow me, only dogmeat's puppy will. I've tried hiring then firing him and killing him and neither of these things change the fact that nobody will follow me. For some reason Charon is located in the citadel courtyard. Any one know how I might be able to fix this?

From what i have heard, certain cheracters will only follow you depending on your karma status. Too evil fawks wont follow, neither will RL-3.
Nuetral karma is the best option.

only dogmeat and puppies will be 100% loyal to you. the rest karma may be a factor. if you rob or kill where you pick up a sidekick, they may turn on you.