Tyndareus

Tyndareus was twice King of Sparta. He was the son of Oebalus and brother of Icarius and Hippocoon, all of whom were also kings. He was married to Leda, daughter of the Aetolian king Thestius. He was the father of Clytaemnestra,Castor, Timandra, Phoebe, and Phylonoe and foster-father of Helen and Pollux, whose father was Zeus.

First Reign
Tyndareus' first reign was very short as he was deposed by Hippocoon and his sons. He fled with Icarius into exile. However, he was reinstated as king by Heracles.

Second Reign
Tyndareus' second reign was shared by Icarius, who reigned as co-king. He accepted Zeus' children by Leda as his own and married his eldest daughter, Clytaemnestra, to Agamemnon, King of Mycenae, who was recently exiled from Mycenae by his uncle Thyestes, who usurped the crown. He deliviered military aid to Agamemnon to help take back the kingdom.

His youngest daughter was abducted by Theseus and later married to Menelaus, who succeeded him in Sparta, thus ensuring the dominance of the Atreids in the Peloponessus. He held a contest to decide Helen's groom, with several eligible princes and kings arriving as suitors in his palace. However, he was worried war would break out among the unsuccessful suitors after he announced the winner. He consulted Odysseus, who suggested an oath which made them swear to unite to defend Helen's husband should she be taken away from him. He, in return, negotiated with Icarius for his daughter,  Penelope's hand in marriage to Odysseus. He died shortly before the Trojan War broke out, succeeded by Menelaus.