Where exactly are you renaming them? If you're just opening up Household Management, clicking on their file in there and renaming the household that way, you're not actually renaming them, just their file name. You can still do it from there though. Click on them in Household Management and choose 'edit', the icon that looks like a pencil. It'll take you to CAS. From there you can rename the household last name or even their first names, whatever you desire. Once you save from there the new household name should stick. Good luck! :)