He was a physician, and brother to St. Gregory Nazianzen. When the latter repaired to Caesarea, in Palestine, where the sacred studies flourished, Caesarius went to Alexandria, and with incredible success ran through the circle of the sciences, among which oratory, philosophy, and especially medicine, fixed his attention. In this last he became the first man of his age. He perfected himself in this profession at Constantinople, but excused himself
from settling there, as the city and the emperor Constantius earnestly requested him to do. He was afterwards recalled thither, singularly honored by Julian the Apostate, nominated his first physician, and excepted in several edicts which that prince published against the Christians. He resisted strenuously the insinuating discourses and artifices with which that prince endeavored to seduce him, and was prevailed upon by the remonstrances of his father and brother to resign his places at court, and prefer a retreat, whatever solicitations Julian could use to detain him. Jovian honorably restored him, and Valens, moreover, created him treasurer of his own private purse, and of Bithynia. A narrow escape in an earthquake at Nice! in Bithynia, in 368, worked so powerfully on his mind, that he renounced the world, and died shortly after, in the beginning of the year 369, leaving the poor his heirs. The Greeks honor his memory on the 9th of March and in the Roman Martyrology he is named on the 25th of February.
(Source: Butler’s Lives of the Saints)