Cepheus and Cassiopeia allowed Perseus to become Andromeda's husband after he used Medusa's head to turn Phineus and his men to stone for plotting against him.Ovid, Metamorphoses 5.1–238 According to Hyginus, the betrothed of Andromeda was named Agenor.Hyginus, Fabulae 64 After spending a year or so at the court of his father-in-law, Perseus finally set off for Seriphos with his wife. Since Cepheus had no heir of his own, the departing couple allowed him to adopt their first-born child, Perses, who was destined to give his name to the Persians. Cepheus was later made into the constellation Cepheus.
