Phokus and his brother Priasus were the sons of Kaeneus and were listed among the Argonauts in Hyginus' Fabulae. Other than the part mentioning the Argonauts assembling, the brother are not mentioned in Fabulae.
Kaeneus & Unknown Woman
"Phocus and Priasus, son of Caeneus, from Magnesia."
- Hyginus, Fabulae, 14