I like some aspects of your idea. I'm always trying to do something this waw, about familiar ties, like I did with Yeux in Beluaterra, when he married and ruled with a Regent Queen in his place, now is up to the player to enforce the name Sarpentis.
And I did the same in Sirion, where we have at least one player playing with a daughter of Erik Eyolf... and he's trying to marry once again. In the past, when I had more people related to him, I tought about open a guild. But, with time, people left the game and he have less daughters, sons and lovers in the last months.
I don't think my character in Dwilight have the same power to start a Great House... and you must consider build a "general" uild where you can gather people from different Great Houses.
