I haven't completed the gong yet.

They simply have no parents in their pic in the Details, just like adults don't, only these are children. There wasn't any kind of event, no-one is missing from the village, so their parents are still present, I just don't know which of my villagers they were!

All the children affected are the same age, so they must have had different parents, as none of them are twins. My total population is only around 49, so there's a limited shortlist of mothers, but fathers....well, it could have been anyone lol

Edit: yes the children-in-a-barrel event is a possibility; I don't remember it happening though, but it would explain a group of children all the same age