In Greek mythology, Zethus (Ancient Greek: Ζῆθος) was the twin son of Zeus and Antiope, brother of Amphion, and co-founder of Thebes' walls. A hunter and herdsman of great strength, he carried stones by force while Amphion moved them with the lyre; together they punished Dirce and Lycus and ruled Thebes before the return of Laius.
Adapted from Wikipedia, "Amphion and Zethus" · CC BY-SA 4.0
I.Childhood and revenge
Antiope fled in shame to Sicyon after Zeus raped her and married King Epopeus. Nycteus or Lycus attacked Sicyon to reclaim her; on the way back she gave birth to the twins and was forced to expose them on Mount Cithaeron. Lycus gave her to his wife Dirce, who treated her cruelly for many years.
Antiope eventually escaped and found her sons living near Cithaeron. Convinced she was their mother, they killed Dirce by tying her to the horns of a bull, gathered an army, conquered Thebes, and either killed Lycus or forced him to yield the throne.
II.Builder of Thebes
Zethus became a hunter and herdsman devoted to cattle breeding; his attribute was the hunting dog, while Amphion's was the lyre. At Apollo's command the brothers built the walls around the Cadmea. While Zethus struggled to carry his stones, Amphion played and the stones glided into place. Zethus married Thebe, after whom the city of Thebes was named (or the kingdom was named for their supposed father Theobus).
III.Later misfortunes
Zethus is said to have had only one son, who died through a mistake of his mother, causing Zethus to kill himself. In the Odyssey his wife is Aëdon, daughter of Pandareus, who killed their son Itylus in madness and became a nightingale. After the deaths of Amphion and Zethus, Laius returned to Thebes and became king.
Elements of the brothers' myth are often compared to the Dioscuri and to Romulus and Remus as city founders.