In Greek mythology, Cepheus was king of Aethiopia (sometimes localized at Joppa), husband of Cassiopeia, and father of Andromeda. Compelled by oracle to expose his daughter to the sea-monster after the queen's boast against the Nereids, he later gives the rescued princess to Perseus and adopts their son Perses. Distinct from Cepheus son of Aleus, the Tegean Argonaut.
Adapted from Wikipedia, "Cepheus (father of Andromeda)" · CC BY-SA 4.0
I.Kingship and parentage
Cepheus is son of Belus, Agenor, or Phoenix according to the stemma. When Belus is father, Achiroe daughter of Nilus is mother and Danaus, Aegyptus, and Phineus are brothers. Hyginus names him son of Phoenix and king of the Ethiopians. Some traditions place the court at Joppa in Phoenicia, named from Iope.
His brother Phineus (or Agenor in Hyginus) is Andromeda's first betrothed—the rival Perseus will turn to stone with Medusa's head.
II.Andromeda and the stars
After Cassiopeia's boast, Poseidon sends flood and Cetus; the oracle of Ammon at Siwa demands Andromeda as sacrifice. Cepheus binds her to the rock. Perseus bargains for marriage, kills the monster, and when Phineus plots against the wedding, petrifies the conspirators. Before departing for Greece, Apollodorus has the couple leave Perses with Cepheus—eponym of the Persians in Greek folk etymology.
Zeus sets Cepheus among the constellations beside Cassiopeia, Andromeda, and Perseus. The atlas id cepheus-ethiopia separates him from the Arcadian Argonaut Cepheus.