Saint Gregory the Theologian (329- 391 AD) Archbishop of Constantinople, on January 25 Saints Gregory the Theologian , also known as Gregory of Nazianzus and Gregory the Younger , was a great father and teacher of the Church. His father, whose name was also Gregory, his mother, Nonna, his brother Caesarius, and Gorgonia, his sister, are all honored as Saints. His extant writings, both prose and ...