I am an old maid by Roman standards. Nineteen and not even a suitor? What a tragedy. This realization struck me not so long ago and led me to consider ages in books (because everything leads back to books with me).
Lots of people seem prone to criticizing ages in fantasy. They say “he/she’s not old enough for that kind of responsibility/maturity/what have you.” It makes sense in our modern context, especially after hanging out in a high school cafeteria or even a college lounge for more than an hour, but it’s just that—context.
30 is the new 15.
People all the way until the last century didn’t live as long as we did. Most of them were dead by the time they hit forty or younger. That means twenty was about middle aged and you had best get to work building empires and fighting battles and making babies before then or the human race was going to go extinct.
When kids rule the world.
Queen Victoria was eighteen when the throne passed to her. The infamous Battle of Crecy provided Edward the Black Prince the chance to lead men and win his spurs at sixteen. Joan of Arc handed the English their backsides and saved her country even though she never reached twenty. Before he got to double digits, a certain Austrian boy was already hashing out melodies on his violin and Isabella the She-Wolf showed remarkable political maneuvering when she was just twelve—enough to get favorites of the king banished.
With this in mind, I see no reason a fantasy character can’t command armies or take a crown or become the most powerful mage their respective world has seen when they just hit mid-teens. When a writer wants to explore certain themes, audiences might cringe and be uncomfortable if the character is what they consider too young, but that does not mean someone younger couldn’t have the same reactions and experiences.
Just to clarify…
I don’t think it has to do with when a person was born, I think it has to do with how they were brought up. (Heck, crazy little me was able to raise a baby donkey by myself at eight. Yes, he survived and lives to bother me to this day.) When children have people around them who expect them to be a grown ups by a certain time, overall they tend to meet those cultural norms. Therefore, I see no reason that epic fantasy heroes/heroines can’t keep on being teenagers.
Because we tend to have much different standards in the Western World today doesn’t mean younger people couldn’t be capable of the grand and glorious deeds that are often attributed to them in fantasy. It depends on the person and it depends on what kind of setting they come from. So long as a writer sets it up properly, I see no reason a character can’t have a whole series in adventures before they’re out of their high school years.