Distantly related to the imperial family of Constantine, he owed his progression from a less significant Levantine bishopric to the most important episcopal see to his influence at court, and the great power he wielded in the Church was derived from that source.
It was of particular interest that Eusebius was nearly persecuted because of his close relationship to the Emperor Licinius while serving as Bishop of Nicomedia during Licinius' reign.