I believe the Wookie won't join your group if your pc is a LS.
The Handmaiden won't join your group if pc is a female.
The Disciple won't join your party if your pc is a male.
Some of your party members can become Jedis if you want to train them.
I am not too sure about the list below, but maybe some one will correct me.
T3-M4, expert Droid
Kriea, Jedi Consular
Atton Rand, Scoundrel (can become a Jedi Sentinel)
Bao-Dur, Tech Specialist (can become a Jedi Guardian)
Handmaiden, Soldier (can become a Jedi Guardian)
Mira, Scout (can become a Jedi Guardian)
Hanharr, Wookie Scout
G0-T0, expert doid
HK-47, combat droid
Mandalore, soldier
Disciple, soldier (can become a Jedi Consular)
Visas Marr, Jedi Sentinel
Prestige Class starts once you are level 15. Talk to Kreia.