Sure. We can do all that in the OOC. Also - I think Tywin would be a great character to have. Cersei's taken over Kings' Landing, following Roberts death (for which Cersei is one of the main suspects in the beginnign of the RP), and I'd love to see their banter and just general disagreements; the way he attempts to control her and how she tries to fight it.
I also think Ned would be a useful character to have, I can't remember if anyone's taking over him, and if they are then maybe Cat?
I'm only starting off with the one character, but basically bringing anyone into the mix would be a good idea. However, 3 characters' aren't necessary.