Probably a interesting idea in a non-MMORPG setting, while well thought out I'm not sure this game needs it. Currently the only other game that has something planned like this would be, Chronicles of Elyria. Please take a read I posted the link below while not exactly Wurm it is unique and might be the first MMORPG system developed around the notion. With Wurm's background it just doesn't seem likely for them to implement something so large with the team being on the slow side to make improvements. It took us years to experience bridges, I shudder to think about families. The two games you cited are single player games, I've played them both. But I commend you for a well executed suggestion, and I hope you forgive my point of view.
https://chroniclesofelyria.com/blog/414/Design-Journal-5--Families--Family-Selection
