Wikipedia
In Greek mythology, Tyndareus was a Spartan king, son of Oebalus (or Perieres) and Gorgophone (or Bateia), husband of Leda , father of Castor, Clytemnestra, Timandra, Phoebe and Philonoe, and stepfather of Helen of Troy and Pollux.
Tyndareus had a brother named Hippocoon, who seized power and exiled Tyndareus. He was reinstated by Heracles, who killed Hippocoon and his sons. Tyndareus’ other brother was Icarius, the father of Penelope.
Tyndareus’ wife Leda was seduced by Zeus, who disguised himself as a swan. She laid two eggs, each producing two children.
When Thyestes seized control in Mycenae, two exiled princes, Agamemnon and Menelaus came to Sparta, where they were received as guests and lived for a number of years. The princes eventually married Tyndareus' daughters, Clytemnestra and Helen respectively.