Ardashir I
Hormizd was the third-born son of Shapur I (). According to folklore, Hormizd's mother was a daughter of the Parthian dynast Mihrak. His two elder brothers were Bahram (the eldest) and Shapur Meshanshah, whilst Narseh was his younger brother. Hormizd had two sisters named Adur-Anahid and Shapurdukhtak. His grandfather was Ardashir I, the founder of the Sasanian Empire. The Sasanians had supplanted the Arsacid Empire as the sovereigns of Iran in 224, when Ardashir I defeated and killed the last Arsacid King of Kings Artabanus IV () at the Battle of Hormozdgan.