Moving out sims

I have a household that currently has 6 sims living there. The parents are now old and I want to move them into a house in the same world so they can live on their own, and have their kids visit them. I keep seeing things about splitting the household or merging but it’s not really making sense. I ended up almost moving them out ig by having them move into a new world but it didn’t tell me where that world was. So now I am confused.

How do I move 2 sims out of a household into their own in the same world??