Saint Caesarius was the younger brother of Saint Gregory of Nazianzus and was extremely famous for both turning down a prominent spot at the court of Julian the Apostate for his faith and for his skills as a physician. After being born in 331 in the villa of Nazianzus in Cappadocia (modern day Turkey) as the youngest son of the Bishop of Nazianzus (Saint Gregory the Elder) he studied at Caesarea Mazaca. After his early education was completed, he then left to study medicine, astronomy, and geometry at the elite schools in Alexandria. Here he was so strong in his studies, especially his study of medicine and physician skills, and quickly became more advanced that the other students. His fame as a physician spread quickly and in 355 AD he travelled to the Imperial capital Constantinople.
As much as he enjoyed living in the thriving capital, he returned home when his brother Saint Gregory arrived (who was travelling home from his journey to Athens). Saint Caesarius found the live at Constantople attrative though, and returned to the city to serve as physician in the Court of Constantius II and then of Julian the Apostate. Julian worked hard to convince Saint Caesarius to abandon his Christian faith and instead return to the pagan ways of the Empire. Though secure and strong in his Christian faith, Saint Caesarius was actually only a catechumen at the time. Rather than denying Christ, he chose to resign from the court.
Under Emperor Jovian he returned as physician and then was tapped as quaestor of Bithynia (a treasurer like position) under Emperor Valens. On October 11, 365, a strong and terrible earthquake struck Nicaea. Though he survived, Saint Caesarius's brother begged him to abandon life at court and instead return home to take up a religious life. Saint Caesarius did get baptized immediately following the accident (as it was common to wait later in life for baptism for Christians in the early Church) but tragically died in the resulting plague that followed the destruction from the earthquake. Saint Gregory had his brother's estates sold and distributed to the poor. Saint Caesarius was buried at Nazianzus and his brother, Saint Gregory, pronounced the funeral oration. Much of what we know of Saint Caesarius comes from this funeral oration, "On His Brother: Saint Caesarius".
Saint Caesarius's feast day is celebrated on February 25th in both the Catholic and Orthodox churches.