Cecil Harvey is the main protagonist of Final Fantasy IV, and, as such, is the only character to remain in the character's control for the entire duration of the game. Cecil is a unique character, as he is one of very few characters in the Final Fantasy series to change class, shedding his Dark Knight persona to become a Paladin. He is also possibly the darkest protagonist in the series so far, an anti-hero responsible committing atrocities in the name of his kingdom, before seeking redemption for his dark past.
In Final Fantasy IV
Cecil is half-Lunarian, a species of people from the smaller moon that orbits around the Earth. His father, Kluya the Lunarian, was killed before his birth. His mother, Cecilia died during childbirth, not living long enough to give her child a name. Cecil's older brother Theodor ran away with him and abandoned him outside of the Kingdom of Baron, where the King found him. Seeing the resemblance between the baby and his mother, the King named him Cecil and took him in as his own child.
The King raised him personally to become a Dark Knight, causing some hostility between Cecil and Kain Highwind. Feeling that the King was treating Cecil too specially, he attempted to fight him, but was stopped by Rosa Joanna Farrell. Since then, the three became very good friends.
In Final Fantasy IV: The After Years
He is married to Rosa Joanna Farrell and has a son named Ceodore Harvey.