Ivan the Great was his father's regent

His father is Vasily II the Dark who was the appellation given to his father during the civil war after his cousin Dmitry Shemyaka blinded him in an effort to seize control. During one of the conflicts, Vasily II, his father, lost his sight. Ivan the Great was just five years old when his father was kidnapped and rendered legally blind by his cousin. He was born in the middle of the biggest civil war in Old Russian history. He appointed Ivan as his co-ruler and regent in order to retake the throne and carry on with his rule. In other words, Ivan the Great was his father's regent at only six years of age.

Ivan was finally revealed to his father's enemies, who had banished Vasili II, after originally being concealed in a monastery and then being transported to safety. In order to insure his succession, his father appointed ten-year-old Ivan as co-ruler after being brought back to the throne with the help of his allies.

In a political arrangement that resulted from his family's purchase of territory, Ivan III was solemnly affianced to Maria of Tver, the daughter of the Grand Prince of Tver, when he was seven years old. In 1452, when he was 12 years old, he married her. For the following ten years, he served as his father's co-regent, learning the ropes of leadership and the art of combat.