It might seem like a good idea to allow one player to play a few different characters, particularly if they're associated somehow, such as being immediate family members. The trouble is this suddenly gives a single player multiple voices in character. And if you're multiple people, you can throw your weight around a lot more, win arguments and votes through weight of numbers, and back yourself up on even the most ridiculous ideas so that it sounds like everyone agrees with you. On the other hand, the need to do all this in character does mean that your player will have to at least make some sort of effort at roleplaying in order to gain this advantage.
Padmé: This is my mother... er... Judy.
Anakin: Pleased to meet you.
Ruwee: And I'm Padmé's father, um... Reuben.
Anakin: It's a pleasure, sir.
Ruwee: So, uh... What do you do for a living?
Anakin: I'm training to be a Jedi. Protecting Padmé is my first solo assignment.
Jobal: Our daughter's a kick-ass Senator! Maybe she's got her eye on... er, I mean, she's protecting you?
Anakin: We're investigating the missing Peace Moon plans.
Ruwee: It's that Governor Bubble, mark my words. Right Jodie?
Jobal: Right, Ruwee.
Anakin: We're going to see the effects of the missing moon and gather evidence.
Sola: You should just arrest Bubble and be done with it.
Padmé: Sola's right! Eyewitness accounts! There's our evidence!
GM: Note to self: Jim does not get to play more than one character.
Padmé: Why not? This roleplaying stuff is easier than I thought.