I know this may sound confrontational but it is just a straight answer, no heat or offence meant. I appreciate the curiosity and the fact that you enjoy the game.
Mix and match is impossible even on a conceptual level. Who is your grandmother going to be married to? Your brother?
Since, when your mother marries someone (M) other than your father, this person becomes your stepfather, who else could she be married to?
So no, no mix and match is possible.