The characters in ff7 are still pretty darn young as well to be doing what their doing. Just not as young as what most rpg's have.

If the games were having their ages be realistic the very youngest people in your group would probably be in their mid to late twenties.

Any younger then that and they wouldn't have the maturity (and in alot of cases the physical strength) to pull off the task at hand.

And the wise advice givers would be in their 40's and 50's instead of their late twenties or early 30's like many rpg's have them.