Khosrow was the supreme ruler of Iran from 531 to 579, a very long reign during which he instituted important reforms and created prosperity that survived after his death. Because of the lasting effects of his reign he gained the epithet Anushirvan, Middle Persian for "the Immortal Soul."
When he succeeded his father, Kavad I, Khosrow was still a teenager. As a child he would have started school young and learned reading, writing, riding, archery, and military strategy. As the youngest of four sons, he would not have been expected to become ruler after his father.
About 520, when the Byzantines and the Persians were fighting without definite victories and therefore making peace treaties, Khosrow's father Kavad suggested to Emperor Justin I (Justinian's father) that Justin adopt Khosrow as a Roman citizen. This was at a time when it seemed highly unlikely that Khosrow would be in the line of succession. This idea of fostering Khosrow at the Byzantine court was a move toward creating more understanding and amity between the two empires. Justin and Justinian were for this, but an advisor warned against it, lest circumstance lead to Khosrow trying to take over the Byzantine throne. Instead they offered to take Khosrow, but only with the rights offered to outsiders, barbarians. Khosrow was insulted, which probably colored his attitude toward the empire to the west.
As it turned out, his three older brothers all had strikes against them that prevented them becoming king.
The eldest, Kawus, was the likeliest heir presumptive, but after a revolt by followers of an offshoot of Zoroastrianism led by a man named Mazdak, and the support that Kawus gave to Mazdak, he was considered disqualified for the succession by the nobles who were all strict Zoroastrians. (Khosrow was a Zoroastrian.)
The next, Jamasp, lost an eye in a battle and was considered unsuitable. The third, Xerxes, led an army that defeated Byzantines in 528 at the Battle of Thannuris. Although a victory, Xerxes was disgraced by Kavad because 500 of his soldiers were killed.
So when Kavad died, Khosrow became the obvious choice. Before we get into the start of his long and impressive reign however, let's take a departure into the invention of two popular table games connected with him. See you tomorrow.