all depends you have to be more specific.
cannot be for example be family to a burgomaster or one of the ruling houses in the port, thats out of the question.
noble you can be but it is often best to make up your own name/clan/family.
i no way can you pretend that your family holds power in the module as that would give you an advantage others do not have and thats not allowed (this part needs better explenation but atm i can't think of a better way to word it)
so depending on what you had in mind yes and no is the awnser.
you can be part of orders that are not represented in game yet, if they are represented ingame and there no players in it ask a dm for the rp if there are players in it go to the players, theres often 1 leading it.