Helen of Troy refuge with Leda. The swan gained her affection, and the two mated. Leda then produced an egg, from which Helen emerged. The First Vatican Mythographer introduces the notion that two eggs came from the union: one containing Castor and Pollux; one with Helen and Clytemnestra. Nevertheless, the same author earlier states that Helen, Castor and Pollux were produced from a single egg. Pseudo-Apollodorus states that Leda had intercourse with both Zeus and Tyndareus the night she conceived Helen. On the other hand, in the "Cypria", part of the Epic Cycle, Helen was the daughter of Zeus and the goddess Nemesis.
Leda (mythology) not see her brothers among the Achaeans. The narrator remarks that they are both already dead and buried back in their homeland of Lacedaemon, thus suggesting that at least in the Homeric tradition, both were mortal. Another account of the myth states that Nemesis (Νέμεσις) was the mother of Helen, and was also impregnated by Zeus in the guise of a swan. A shepherd found the egg and gave it to Leda, who carefully kept it in a chest until the egg hatched. When the egg hatched, Leda adopted Helen as her daughter. Zeus also commemorated the birth of Helen