Mighty countries have often been ruled by children who were grade-school age, or even younger! Take a look at the cute little faces of monarchy gone wrong.
LOUIS XIV, AGE 5
Just a year after Louis became King of France in 1643, the Venetian Ambassador wrote, “He knows that he is King and wants to be treated as such.” At 7, he signed his first decree with his own hand, granting amnesty to defected enemies.
At age 10, when other boys liked to pretend they were kings, Louis would make-believe he was a valet! He ruled for 72 years.
LOUIS XV, AGE 7
The great-grandson of Louis XIV, this Louis liked to pretend he was a cook. Shortly after he became King in 1715, he hid behind a curtain to avoid giving an audience to an ambassador.
Those caring for the young King were so concerned about assassination they kept his food under lock and key – and stored his handkerchiefs in a triple-locked safe, fearing someone would lace them with poison.
KING TUT, AGE 8
The Egyptian ruler assumed the throne in about 1366 B.C. It is unclear on who his parents were, but historians believe his uncle was the ruler Akhenaten. Tutankhamun spent his eleven years as ruler reversing the monotheistic changes his uncle had made to the Egyptian religion.
King Tut died at the young age of nineteen, apparently from gangrene contracted from a broken leg.
Actually it only SEEMED that the children ruled, usually there was a group of elders either royal or church, stately advisors, or other such people that told the child what to do. For example, Ivan the Terrible who's father died young and who's mother was poisoned when he was just 8 and then of course left to rule, but contrare mon frere! It was the Boyars that guided him until his great victory as a teen at the Battle of Vaslui.
Then because they'd been such great teachers the Boyars found out what a tyrant they'd created when the boy czar returned a man and a full-on ruler.
To me, real history really is much more interesting sometimes as it really happened such as Ivan the Terrible killing his own 1st born son, Ivan Ivanovich (by accident?) over nothing more than parting his hair wrong (or was it because he wouldn't divorce his wife and marry another for political reasons? The story is gray -we may never know).
But yes, it does seem that the rulers who began their reigns at an early age were destined for the greatest fates and most interesting lives compared to those who took over in later years.