Other elements are mine.
The story of Leda and the Swan comes from the Greek mythology. It tells the story about the beautiful woman Leda. The god Zeus saw her and fell immedately in love with her. She was already married, but Zeus came to her in the form of a swan and seduced her.
Leda got two eggs. The first egg contained Castor and Clytemnestra and the second egg contained Helen of Troy and Pollux.