Unlock Aaron:
In chapter 6, go to the top foor of the Hotel, one room before Zanetti. You must at least have the Governor title.

Unlock Gina:
In Chapter 5, go to the wharf and warehouse 12. Beat all of the thugs with weapons. Go to the storage room and rescue her.

Unlock Jason G:
In Chapter 4, go to the gas station. There will be 3 gang members. Beat them, and a cutscene with Jason plays. Beat him and he'll join.

Unlock Lola:
In Chapter 2, beat any five Fatimas Saints. Then go to the police station and into the cell area. Lola will be trapped inside. Rescue her.

Unlock Raven:
In Chapter 4, go to the southside park. Raven may appear and challenge you to a fight. Beat him. You only have one chance.

Unlock Norma:
You must beat Norma in every chapter to unlock her. In Chapter 3, she is located outside the Hole. In Chapter 4, you must to enter the Station Zone from the South, without a vehicle. She can be found in the Station Zone again in Chapter 5. In Chapter 6, you must exit Industrial Area South from the East. She will approach you in the Town Square area. Beat her there. Finally, go to the Hotel Zone. She will call you and tell you to meet her at the basketball court. Go and beat her there, and recruit her. If you miss any encounters, you'll have to start a new game.