User blog comment:Commander Marko/Who's the prettiest of them all?/@comment-4057638-20140702071124/@comment-3974211-20140702180205

The fact she looks young, sounds young and acts young. I'd put her at ~15, but I'd be more inclined to say younger than older. She sounds like a child pretending to be mature, but without any of the grit Ashe's old voice had which proved her experience.

Jinx has been confirmed as older than Vi - Jinx's growth is clearly stunted, despite how young she looks.