Make the option of adopting always available.

College emails should become more frequent, with events added. Like, you have the option of sending money if they want/need something. Or they come to visit for a few weeks. Or they send gifts/money. I also like the idea of writing back to the family.

It'd be nice to be able to choose the house at the beginning when you're adopting the character. Maybe give like ten options of houses.

If one parent dies before the other, leave the option for a child to take over the house with the parent still in it. Similarly, if a child is still underage when a parent dies, have an older sibling take care of them.

Have family reunions (or holiday and birthday parties) in the second generation where the old siblings come to visit for a little while.

I agree about better interaction with pets. And maybe they have different effects on the family. Calming, happiness, sadness if a pet passes away, etc..

And I also like the remarriage idea. If a player's adoptee becomes a widow they should be able to find a new spouse. You could also put the option of divorce. And maybe marrying someone who already has kids.

Also, it would RULE if you could make expansion packs eventually (or right now!) New trophies, new challenges, new suprises.