[@KatherinWinter]

I'm not the GM, but it looks to me that they need to at least be 18, judging by the human character sheet that the GM posted.

If you're still not sure, though, the link in the first OoC post (the one that says cultural exchange between species bill) might have something for you to go off of.

EDIT: Apparently anyone is allowed as long as they've been approved/can deal with however many other host family members they have. So if you want to play a teenager, for example, you can, as long as they've been approved and/or have proven that they can deal with however many host family members they've been dealt. Or something along those lines; not 100% sure, honestly.