Khosrow was the son of Bahram IV (r. 388–399), the sixteenth king (shah) of the Sasanian Empire.
[1] Bahram V, another son of Yazdegerd I, opposed the decision of the nobles, and asked the Lakhmid king of al-Hirah for military assistance, which he received.
At the head of an army of numerous soldiers, Bahram marched towards Ctesiphon, where he promised that he would not reign like his father Yazdegerd I did.
According to the Shahnameh ("The Book of Kings"), Bahram suggested that the royal crown and attire should be placed between two lions, and the person that retrieved them by killing the wild animals should be recognized as the shah of Iran.
Khosrow chose to pull out, whilst Bahram withstood the trial and won the throne.