Nuka Cola Kidd
Super Freak
Actually, they will speak to you about the loyalty quest even if you never speak to them beforehand. Chambers will notify Shepard whenever a character "wishes to speak with you". I'm wondering what the actual prerequisite might be, as I want to avoid doing unnecessary missions on my Insanity playthrough.
I think its by the set. You get the first set and after Horizon you get their loyalty missions, along with the new set of members.