That's a good perspective, madster. It sounds like a good way to implement it: families contain "base" variables, effects and behaviors, and objects in the family inherit them. The current "only those in common" is pretty obscure and was retro-fitted in after the main engine was written.
I wonder if we could even throw in encapsulation? Eg. variables only accessible by the object that owns them. Would that be useful in the real world? And polymorphism... can't think of a decent way that would fit in to events.