"child" is defined differently in different cultures. Here in the US, under 18.

In some cultures, a girl menstruates, she can conceive, she's not considered a child.

I think it's somewhere in between.

Also, individuals mature much differently

For example, two kids both 13, one acts 10, the other acts 17; one looks immature, the other looks much older than his age.

Knew a Guatemalan guy, 16, had 3 kids already, wife had 1st child at 12, I said wtf, he said in Guatemala it's the norm

Marriage at 12, 13, and couple kids by 15