Well, it's actually Vivi ( he's 9 ) but it's okay
Vivi isn't 9, he's just described as having the physical stature of a 9 year old. He shouldn't count being has he was created from Mist, not born, but the more accurate number is 6 months - that's how long Quan raised him before he came to Alexandria, and he was created right before Quan found him.

But none of that matters anyway, because even in that game Eiko is 6. Don't know if there was ever anyone younger than that.