In Antigone by Sophocles, Haemon is the son of Creon and Eurydice. As Creon is the brother of Jocasta, and Antigone is the daughter of Jocasta, that makes them cousins. Haemon and Antigone are engaged to be married. Somewhat unsually for the period, given that marriages were normally arranged for economic convenience, Haemon appears to be deeply in love with Antigone.
At the end of Scene 6, Creon decrees that Antigone be walled up alive in a cave with just enough food so that he cannot be directly blamed by the gods for her murder. Between the end of Scene 6 and the beginning of Scene 7, Antigone kills herself. Next, a messenger reports:
MESSENGER: Haemon is lost. His blood was spilled by a familiar hand.
CHORUS: By his father's or his own hand?
MESSENGER: Himself, angry with his father for the murder.
Thus it is clear from the text that Haemon commits suicide.