Phocus was the son of King Aeacus of Aegina and the Nereid Psamathe. Psamathe was chased by Aeacus and tried to evade him by transforming into a seal; Aeacus then raped her while having the form of a seal, and that's how Phocus was conceived. His consort was Asteria, with whom he had twin sons, Crisus and Panopeus.
Phocus was the favourite son of Aeacus; his other sons by Endeis, Telamon and Peleus, were jealous of this favouritism, and instructed by their mother, plotted in order to kill their half-brother. Telamon told Phocus that they were organising a pentathlon, and that he should participate as well. During the games, Telamon pretended to throw the discus but "accidentally" hit Phocus on the head, instantly killing him. Telamon and Peleus then tried to hide the body, but were discovered by their father, who exiled them from Aegina.
A different Phocus also appears in Greek mythology, who was originally from the region of Boeotia. He had a beautiful daughter, Callirhoe, who had thirty suitors. Phocus was hesitant as to who would be the best husband for his daughter, and when he said that he would get advice from the Pythian oracle, the suitors got angry and killed him. Callirhoe managed to escape, and when a festival was held sometime later, she revealed how her father was murdered. The people helped her by declaring war on the murderers, who were successfully hunted down and stoned to death.