Gregory of Nazianzus, so called, was born during the episcopate of his father, Gregory, bishop of Nazianzus.  Gregory the elder died in 373, after holding the see forty-five years.  The birth of Gregory the younger cannot therefore be put before 328, and Basil was a little younger than his friend.  (Greg. Naz., Ep. xxxiii.)  But the birth of Gregory in his father’s episcopate has naturally been contested.  Vide D.C.B. ii. p. 748, and L. Montaut, Revue Critique on Greg. of N. 1878.