Lelex was a demigod and a son of Poseidon.
His grandson (fathered by Myles) was Eurotas. Eurotas had a daughter named Sparta, who would later marry Lacedaemon. Lacedaemon named the city of Sparta after his wife; however, the city's name would also be his own, as it was called either Lacedaemon or Sparta interchangeably.
Perseus is a descendant of Lelex. Lelex’s great-granddaughter Sparta gave birth to a daughter named Eurydice (no relation to Orpheus’ wife Eurydice), who had married Acrisius, the king of Argos. Eurydice became the mother of Danaë, thus making her Perseus’ grandmother.
Lelex founded the Leleges, a mythical people that lived on both sides of the Aegean Sea.