Diomedes’ grandfather was Oeneus, king of the city of Calydon in central Greece. Diomedes’ father, Tydeus, was forced to flee Calydon after killing one of his relatives, possibly his uncle or brother. In Argos he married Deipyle, daughter of King Adrastus, who bore him Diomedes. Tydeus’s fate mirrored that of Polyneices, the son of the Theban king Oedipus, who also left his homeland for Argos and married a daughter of Adrastus. Tydeus supported Polyneices in his attempt to seize the throne of Thebes from his brother, Eteocles, but the expedition was a disaster and both men died. Diomedes’ father was Tydeus who was exiled from the city of Calydon, and his mother was Deipyle of Argos. Tydeus participated with his army in the famous expedition known as “Seven Against Thebes”, during which he was killed.