Birth

Zeus in the form of a swan consorted with Leda, and on the same night Tyndareus, king of Sparta, also made love to her. This is why she bore, beneath the peak of Mount Taygetus (in Laconia) Polydeuces and Helen to Zeus, and Castor ₁ and Clytaemnestra to Tyndareus. Because of their different parentage, Polydeuces was immortal, and Castor ₁ mortal.

Abduction of Helen

When Helen became a woman, Theseus carried her off and brought her to Aphidnae in Attica. Some say that Iphigenia, otherwise called daughter of Agamemnon and Clytaemnestra, was daughter of Theseus and Helen, but others have said that Helen was untouched when she returned to Sparta.

Campaign against Athens

In any case, while Theseus was in the Underworld, having a preposterous adventure along with his accomplice Pirithous, the DIOSCURI marched against Aphidnae, took the city, got possession of Helen, and led Theseus' mother Aethra ₂ away captive. That is how Aethra ₂ became Helen's maid, following her to Troy. She was set free at the end of the Trojan War by the sons of Theseus.

Abductions

When the DIOSCURI decided to get married, they carried off the daughters of Leucippus ₂ (son of King Perieres ₁ of Messenia, son of Cynortes, son of Amyclas ₁, son of Lacedaemon, son of Zeus and Taygete, one of the PLEIADES), and having wedded them, they had children by them.

Conflict with Messenians

The DIOSCURI, it is told, were once stealing cattle in Arcadia together with two Messenian brothers, Idas ₂ and Lynceus ₁. They allowed Idas ₂ to divide the spoil, and he cut a cow in four pieces, saying that one half of the booty should be his who ate his share first, and that the rest should be his who ate his share second. And before they could even react to that proposal, Idas ₂ had swallowed his share, and his brother had done the same.

Idas ₂ abducts Marpessa ₁

Idas ₂ is son of Poseidon or of Aphareus ₁, son of Perieres ₁. His mother was Arene, after whom the city in Messenia is called.

Idas ₂ is known for having carried off Marpessa ₁, whom Apollo loved. Her father Evenus ₂, unable to catch Idas ₂, who abducted the girl riding a winged chariot that he had received from Poseidon, threw himself into the river Lycormas which is called Evenus after him. Marpessa ₁'s mother is Alcippe ₅, daughter of cruel King Oenomaus ₁ of Pisa in Elis, whom Pelops ₁ killed.

Idas ₂ fights Apollo

It has been said that when Idas ₂ arrived to Messenia with the girl, Apollo attempted to take her, and Idas ₂ fought against the god until Zeus parted them. So Marpessa ₁ was allowed to choose, and she took Idas ₂ as husband of fear that Apollo might desert her in her Old Age. Idas ₂ and Marpessa ₁ had a daughter Cleopatra ₄, who became mother by Meleager of Polydora ₃, the woman who committed suicide on the death of her husband Protesilaus, the Achaean leader from Phylace in Thessaly, who was the first of the Achaeans to land on Trojan soil at the beginning of the Trojan War.

Lynceus ₁

Lynceus ₁, who is also counted among the ARGONAUTS and the CALYDONIAN HUNTERS, was said to excel in sharpness of sight, so that he could see things underground.

Death of all brothers

On account, then, of their disagreement with Idas ₂ and Lynceus ₁, the DIOSCURI marched against Messenia, took the cattle they had lost, and much else besides. And as the DIOSCURI were wainting for their two ennemies to appear, Castor ₁ was discovered and killed by Idas ₂. Polydeuces attacked and chased them, killing Lynceus ₁, but was himself wounded in the head, and fell down in a swoon. Idas ₂ was killed by Zeus with a thunderbolt.

Shared immortality

As Polydeuces refused his immortality while Castor ₁ was dead, Zeus permitted them both to be every other day among the gods and among mortals.

Castor ₁ was the one of the twins who was mortal. An expert in the martial arts, he taught Heracles ₁ to fence. Some say that Castor ₁ was killed by Idas ₂, but others say by Lynceus ₁. Still others say that Castor ₁ was slain in Aphidnae in the course of the war that the DIOSCURI and the Lacedaemonians fought against Athens. It is also said that Idas ₂ and Lynceus ₁ attacked Sparta, and that Castor ₁ died on this occasion. (Castor ₂ was a companion of Aeneas in Italy.)

Polydeuces refused to accept immortality while his brother was dead, and finally shared life and death, every other day, with his mortal brother Castor ₁. Polydeuces learned the art of boxing, and being with the ARGONAUTS, he was challenged by King Amycus ₁ of the Bebrycians in northern Asia Minor, who compelled strangers to box as a way of killing them, but Polydeuces killed him with a blow.