I appreciate the hack very much, but in my case, the two families in the duplex are blood-related families and I think this won't stop them from using one another's houses, losing one another's babies and leaving messes in the wrong kitchen or having the husbands sleep with the wrong twin sister.
I hope there is a fix for my problem.
This will help others where the families are not related.

I have some of those too that I want to put in apartments.
If you can hack for my particular problem I will look for your message.
BTW I have and will have all EPs
Again, thank you Squinge