Alle Kunst ist der Freude gewidmet

I think the evidence in Jugdral appears to indicate an AC of 15 and maybe a little lower. I mean, Dew is about 13, and he's one of the characters who can father children, and others in the breeding pool are 15 or so at the outset and can't be more than twenty by the time everything goes to hell... by which time they can have up to two kids apiece. Fifteen definitely seems to be the age of maturity per FE5, as Leaf is considered old enough to command at that age.

Archanea, though... really, it seems like 16 is the minimum, both for command and for marriage. Yumina and Yubello, at 13-14, are deemed children.