I was thinking of role-reversal of sorts, with a younger kid being in charge for their older sibling, niece/nephew or even parent (we can add "step-", to all this if you feel uncomfortable with blood relatives), based on assumption that "men should always be in charge" or "girls get mature much earlier", etc. (I'm fine with either gender being the "superior").
Similar concept on larger scale can be used in a plot like "same-sex school turns unisex", animes love such stories.
On a different note, I really like that plot:
https://animeotk.com/gallery/showpho...-nanny/cat/608 (needs some adjustements, though), and most pf Psyches commissions, really.