Half-Olympian son of Zeus by Antiope daughter of Nycteus; twin of Amphion. Conceived when Zeus appeared to Antiope in satyr-form (per Apollodorus 3.5.5); Antiope fled to Sicyon, was brought back, and bore the twins on Mount Cithaeron during the journey. Exposed and raised by a herdsman. Diverged from his musical brother Amphion in temperament — Zethus the practical hunter-herdsman, Amphion the contemplative musician. The brothers' debate over the active vs. contemplative life is the structural axis of Euripides's lost Antiope (c. 410 BCE), preserved in fragments and reconstructed from Plato's Gorgias 484e-486d quotation; the dichotomy becomes foundational for the Greek philosophical reception of the bios theoretikos / bios praktikos opposition. After recognition by Antiope, the twins killed Lycus and tied his wife Dirce to the horns of a wild bull in vengeance — the canonical Dirce-bull tableau preserved in the Farnese Bull sculpture (now Naples Archaeological Museum), one of the largest surviving ancient sculpture-groups. Took the kingship of Thebes; built the second walls of the city, with Zethus carrying the stones while Amphion charmed them into place with the lyre — the canonical division-of-labor that exemplifies the active/contemplative dichotomy. Married Aëdon daughter of Pandareus; Aëdon's envy of Niobe led to the accidental killing of their son Itylus and her transformation into a nightingale (the etiology of the nightingale's lament). Death-narrative is variant — some accounts have Zethus dying of grief, others give him a lifespan parallel to Amphion. Pausanias reports the Theban tradition pointing to the joint tomb of the twins north of Thebes, with seasonal soil-transfer rites between Tithorea (Phocis) and Thebes.