The unhappy history of the house of Atreus was one of the most frequently treated subjects in Greek drama. This noble family had a curse on it which resulted in incidences of adultery, murder, betrayal, vengeance, and even unintentional cannibalism. These regrettable events occurred throughout successive generations of the family beginning with Tantalus, the founder of the house, through the Trojan War, and ending with the siblings Orestes and Electra.
Tantalus was a son of Zeus. He angered the gods and was fated to spend eternity in Hades (the underworld) with a boulder hovering just over his head, always about to fall. Pelops, Tantalus’ son, incurred a curse on his family by betraying and killing a friend who had helped him win his wife. Seemingly unaffected by the curse himself, he fathered Thyestes and Atreus, who would become king of Mycenae. There was then a feud between the brothers (Thyestes was accused of seducing his brother’s wife) which resulted in Atreus inviting his brother to a feast at which two of Thyestes’ slaughtered sons were served to him in a pie. Thyestes had a third son, Aegisthus, who got his revenge by killing Atreus and later having an affair with Atreus’ daughter-in-law, Clytemnestra.
This brings us to the characters in Euripides’ play. Atreus had two sons: Agamemnon, King of Argos and Menelaus, King of Sparta. Menelaus married Helen, a daughter of Zeus, while Agamemnon married her sister Clytemnestra (who did not share Helen’s divine father). Menelaus and Helen had a daughter, Hermione, and Agamemnon and Clytemnestra had two daughters, Iphigenia and Electra, and a son, Orestes.
The misfortune of the house continues with Helen being stolen by Paris, a prince of Troy. This causes Menelaus and his Greek allies, including his brother Agamemnon, to declare war against Troy. In order to turn the unfavorable winds before sailing to Troy, Agamemnon sacrifices his daughter Iphigenia to the gods. The sacrifice of their daughter horribly angers his wife Clytemnestra. The Trojan War lasted ten years, during which time Clytemnestra took Agamemnon’s cousin, Aegisthus (surviving son of Thyestes) as her lover. When Agamemnon returned victorious from Troy, Clytemnestra and Aegisthus killed him and assumed rule over his kingdom. At Apollo’s command, Orestes revenged his father by killing his mother and her consort with the help of his sister Electra. Clytemnestra cursed her son to be haunted by the Furies who avenge matricide, and it is these creatures that cause the madness which afflicts Orestes at the beginning of Euripides’ play.