Who was Leda in Roman mythology?

Leda was the daughter of King Thestius, and the wife of King Tyndareus. The god Zeus (Jupiter in Roman mythology) appeared to her as a swan, and seduced her. Since she also slept with her husband, two of her children were mortal, and two were immortal. They were also hatched from eggs. Her children were Helen (better known as the beautiful Helen of Troy), Clytemnestra, Castor and Pollux (also known as Polydeuces). Between Castor and Pollux, Pollux was usually the immortal one.