Re: Changing Sims Between Your Own Housholds
Save each of the households to the Library. Then split each sim into their own household. After that, you can select them from the library and add them to the same household.
Save a Sim or Household to the Library:
Enter CAS with the family, either via Household Manager or in Live Mode by clicking a mirror for example. In CAS you can then save the household in the current state to your library (there should be an icon looking like a folder with an arrow I believe).