Alcmene is the mother of the hero Heracles. She is the daughter of Electryon, the son of Perseus, and Anaxo. Alcmene married her cousin, the general Amphitryon. Because of an accidental murder, the two were forced to flee to Thebes, where they were received by the king Creon. Before sleeping with her husband, Alcmene demanded that her husband avenge her brothers' deaths at the hands of pirates. While battling these pirates, Zeus deceived Alcmene and slept with her. On his return, Amphitryon was outraged to find his wife no longer a virgin. The Theban seer Tiresias absolved Alcmene from guilt, and Amphitryon slept with her as well.
In time, Alcmene gave birth to twins, Alcaeus and Iphicles, after seven days of labor. The birth was delayed by Hera, who convinced her daughter Eileithyia, a goddess of childbirth, to not allow the birth at all. When Eileithyia was tricked and the twins born, Amphitryon did not know whether the boys were his own or Zeus'. After killing two snakes, it was discovered that Alcaeus was a child of Zeus, and Iphicles was a child of Amphitryon. On the advice of Tiresias, Alcaeus was then renamed Heracles, the 'glory of Hera.'
After the death of her husband Amphitryon, Zeus married Alcmene to his son Rhadamanthys.
Ovid. Metamorphoses. (for the story of the delayed birth)