[2] Although his father was from an equestrian family,[citation needed] Macrianus Minor's mother was of noble birth and her name, possibly, was Iunia.

According to the often unreliable Historia Augusta, he had served as military tribune under Valerian.

[3] With help from his father, who kept the imperial treasure, and by the influence of Balista, Valerian's praefect, Macrianus gained the imperial office together with his brother Quietus,[3] through the election by the army, in contrast with the lawful Emperor Gallienus, son and co-emperor with Valerian, who was far in the West.

The two emperors and brothers were recognized in the eastern part of the Empire, having a stronghold in Egypt, the grain supplying province for the city of Rome.

[citation needed] They were however defeated in autumn 261 by Aureolus,[2] and later killed by their own soldiers at the father's request.