Is it possible to open the family tree or relationship of unplayed sims in mccc?

I am also looking for a way to do this!!
What also bothers me a bit is when my sim asks an npc if they're single and they're just dating someone (not married), they will just say "Yes, I'm seeing someone". But I wanna know who! :)

But I play generetions only with one family at a time, and I would love to see the family tree of my sim's boyfriend/girlfriend.
Hopefully someone knows!