I am running out of ideas for households

I actually just filled a spreadsheet with sims I want to add to my base save. I've used characters from three different story lines I want to play out (and Sims from several stories I already played out) and a handful of interesting Sims I made before but never used. They're all connected in some way. But the majority of these Sims already existed, either in game, from cas, or in my mind.
But backstories are essential to set up an interesting save. And connecting those stories makes it even more interesting. You could for example have a feud between aliens and vampires, or, if you don't like supernaturals, Montys and Capps so to speak and integrate side characters into different stories.