I've been looking into what allows child villagers to randomly join overnight, and found a lot of differing thoughts from closer to when the game released. I'm curious if people are more confident in some answer or another now?
If it's main story progress then I don't think that's an issue for me because a friend says he got them before he had all the villages unlocked, whereas personally I've been waiting for a while just before/after dancing for the Kagura Shrines (one person did say they thought children with a certain trait are locked behind a postgame dungeon, but I'm talking just any random child in general). It can't require that you've rescued all the transformed children because of that, either, since there's one in Winter Village, which he wouldn't have been able to get. Myself, I've rescued the Spring and Summer ones, so I do have two villages with one child each (haven't figured out how to get the Autumn/Winter ones). I'd struggle to believe it's pure RNG because I've probably seen around 200 villagers and not a single child. I've tried leaving a lot of open slots in villages, or having 20 villagers and being near cap, though the latter I haven't tried THAT much...? Could it be tied to village level? Mine are all in the 6-8 range, so none are maxed. Could it require having your own children first? I don't have a spouse yet. Could it relate to village happiness or events? I've got a couple villages that have been 100% happiness for a while, though I only recently held my first contest. Could it be tied to skill trees or having certain structures or being a certain character level or doing some specific character's event or just needing a certain number of ingame days to pass (I'm only in my first Summer)? No clue! That's why I'm here to ask--any findings anyone has had would be appreciated!