Like many ancient Greek characters, there seems to be some confusion on what Helen's actual parentage is. In the article
Helen of Troy - Heroine or Goddess?, Karen Pierce concludes that her origins were influenced by Euripides. Leda is often attributed as Helen's mother, but this only came after the playwrite's works. Earlier, it appeared it was Nemesis who was the mother. The stories are very similar:
Pierce: "Commonly referred to as the Goddess of Retribution, ... Zeus also raped Nemesis, and thus Helen was born. In Greek mythology it is not unusual that Zeus should rape his own daughter, he does after all live in marriage with his own sister. This rape, however, caused shame and indignation for Nemesis, and she attempted to flee Zeus' advances by shape-changing into many different creatures, as he pursued her (see Cypria - Athenaeus 8.334B). Zeus finally caught up with her when she was in the form of a goose, and he a swan. After the rape, Nemesis subsequently gave birth to an egg from which Helen eventually hatched. The egg was found and brought to Leda who brought up Helen as her own daughter."
The more well known origin, of course, is that of Zeus descending from the heavens and raping Leda in the form of swan. Personally, neither are very appealing. Sure it's not Cannibal Holocaust or 100 Days of Sodom, but a god descending from the heavens and raping a woman? That has to be terrifying, and calls into question why the Greeks worshipped such a terrifying figure. And a woman laying an egg? Disturbing stuff. One wonders if the movie series "Alien" didn't recall some of this stuff. For the uninitiated, the aliens would attach themselves to a human and implant an egg inside their body. The guy or gal would then wake up oky-doky with the parasite-alien incubating inside their guts. Later, the beast would burst from the chest, squeak, sneer, and run off. To add to this, art depicting Leda shows her being horrified by what she wrought. Pierce: "The pictures that depict Leda with an egg show her discovering it, and often looking surprised or shocked (she sometimes even runs away from the scene). Helen is sometimes shown emerging from the egg as a miniature human, rather than as a baby. "
Pierce concludes, "Although Leda is the traditionally known mother of Helen it is highly probable that the Nemesis version is of older origin.
Prior to Euripides' Helen there is no evidence of Leda having been raped by Zeus in the form of a swan. In fact there does not appear to be any rape story at all associated with Leda and the birth of Helen, until we reach Euripides. This is in contrast to the myth attached to Leda's bearing of the Dioscuri (see Homeric Hymn to the Dioscuri ). Iconographically Leda is seen finding the egg prior to Euripides, and afterwards she is depicted with a swan.
With the Nemesis version of the myth established Helen is revealed to have two divine parents, and thus should be regarded as divine herself.
If Leda does have any valid claim to be her mother, then Helen is the only mortal daughter of Zeus, this is significant in its exceptionality."
