Eleanor of Aquitaine
Eleanor of Aquitaine was fifteen years old in 1137 AD, and not yet married, when her father, the Duke of Aquitaine, died suddenly. Eleanor had no brothers, so she inherited her father's duchy, which included most of southern France.
The High Middle Ages were a violent time, and Eleanor needed a strong military leader to fight the battles that would keep her in power. She found him in the French king, and so the young Eleanor immediately married Louis, the son of the French king. Louis was sixteen. Shortly after they got married, the French king died, and Louis became king. Eleanor moved to Paris with Louis, and had two daughters, but no sons. Eleanor and Louis went on Crusade to Jerusalem together, and Eleanor got to visit Italy, Sicily, and Constantinople as well.
After fifteen years, Eleanor met Henry, a Norman ten years younger than her, and divorced Louis, now the King of France, to marry Henry. She left her two daughters with Louis. Soon, with Eleanor's support, Henry became King of England. Eleanor and Henry had five sons and three daughters (so she had ten children total).
But when Eleanor's second son, Richard, was sixteen years old, Eleanor and Richard teamed up to revolt against Henry. When the revolt failed, and Henry won, he shut Eleanor up in a castle in England and watched her carefully. Eleanor spent most of the rest of her life there, though after Henry died she returned to Aquitaine, and eventually retired to live at a convent there, where she died in 1204 AD, at the age of 82.