Sometimes I feel like Tear was written to be around 20, and then a month away from shipping some publicity guy said "No no no, you can't make the love interest that old, it ruins the self-insertion fantasy for male players pretending to be Luke" so they changed her age. Although to be fair, you can argue her love of cute things is a sign of her younger years peeking through, and the rest can be accounted for by her military training and the steely determination of her personality (hey, she's only a year younger than, say, Yuna).
Anyway! TOTA PLOT DISCUSSION INVADES ANOTHER TOPIC? So guessing time:
Irvine, because he's 17 and from a much worse supporting cast than TotA even to me.