The earlier posts are very strong. In his Poetics, Aristotle argues that the most powerful tragic situations often involve members of the same family, especially when a person is torn between two powerful allegiances, as Haemon is torn between duty to his father and love of his fiance.
Interestingly, Aristotle's only explicit reference to Haemon occurs when he is discussing the four different ways in which what he calls a "deed of horror" may be staged. He concludes his discussion by saying,
of all these ways, to be about to act knowing the persons, and then not to act, is the worst. It is shocking without being tragic, for no disaster follows. It is, therefore, never, or very rarely, found in poetry. One instance, however, is in the Antigone, where Haemon threatens to kill Creon. (S. H. Butcher translation)