It's a fantasy world. Who are you to say when someone should be out of the house? In any case, to the extent Thera is supposed to match "medieval" earth, I'm not sure it's reasonable to expect that everyone be out on their own by age 16. Children typically lived with their parents until married, or possibly with a tradesman if they were apprenticed. Especially in an agricultural community I doubt it would have been uncommon for a male child to live at home, presumably helping with the farm work, on into his twenties. Female children might be expected to leave home earlier insofar as they typically married earlier than men.