Do you use NRaas Traveler? Were you playing a game before this, then did you exit to the main menu, then create a new save in Sunset Valley? Or did you create this save after launching from the desktop?
I ask because TS3 doesn't clear out all memory when you exit a save to the main menu. The NRaas Traveler mod can cause effects similar to what you describe because of this behavior. (The solution is to always quit the game to the desktop before starting a new one; I'm not sure if switching to an existing save is also problematic - I never do either.)
That's the only explanation I can think of. If you quit to the desktop, launch TS3, and create a new save in Sunset Valley, do you still those extra households?
