The EU Rome style of family trees and noble famillies would be perfect. You dont control them but they are still there and you try to care about the characters. It would be dissapointing if you dont implement something like that in the game. And portraits would be nice, doenst have to be like CK 2 but at least to have portraits.
yes seeing other members of your family is important, I would like some sort of basic family interface in their, as you describe.