Constantine V
Leo was the son of Emperor Constantine V by his first wife, Tzitzak of Khazaria (known as Irene upon her conversion), the daughter of a Khagan of the Khazars (thought to be Bihar). Crowned co-emperor by his father in 751 Leo then married Irene, an Athenian from a noble family, in December 769. In 775 Constantine V died, leaving Leo as sole emperor.