Castor is the name of several persons in early Christian records:
1. A correspondent and personal friend of Gregory Nazianzen. There are two letters of Gregory to Castor one (Epist. 93) sent by his young friend and spiritual son Sacerdos, whom Gregory begs he will not detain long. The second (Epist. 94) contains complaints of his own health, and threatens Castor in playful terms if he does not soon send back a lady whom he calls "their common sister."
2. A presbyter of Treves under St. Maximinus, who became a hermit at Caerden, and died Feb. 13 (Acta Sanctorum).
3. A confessor and bishop of Apt, in Provence, who appears to have been born at Nismes, and to have founded a monastery between the years 419- 426. He is commemorated Sept. 21 (Acta Sanctorum, Sept. 6, 249). See Hoefer, Nouv. Biog. Géneralé, s.v.
4. A priest of Coblentz, who is said to have performed many miracles, but his history is uncertain, and his date is unknown (Acta Sanctorum, Feb. 2, 663).
5. The father of pope Felix IV. Castorina was the maternal aunt of St. Jerome. His letter to her (13, ed. Vail.), written when he was in the desert, shows that there had been some disagreement between them.