Champion's Age

In particular, I'm curious how old Kennen is supposed to be as a character. To me I've always pinned him down to being one of the younger yordle's next to Gnar now. About the age of 12/13 or so. It would make the dynamic of his relationship with the other Kinkou's a lot deeper in that he's still learning at this point and is over eager and such. His mannerisms and the way he sounds really helps me point this out as well. No other yordle really sounds as young as he does except for maybe Teemo but Teemo was originally concepted as a child as well so yeah.