I just had a thought, it would be cool if you could organise a family reunion (or maybe it could be an event) and the brothers and sisters of your current generations heir would join the family in the house for maybe a few hours.

Overall though I'd love to see the family side fleshed out even more in the next one....like having grandparents and having brothers and sisters that pop in to see you....maybe even having some neighbors show up for tea :P

The third final idea is maybe having something similar to the stews in Virtual Villagers but you buy groceries and can make different meals for your family depending on what you put in

I like thinking of ideas so I'll make sure to try and suggest more soon