Iŏphon in Harpers Dictionary of Classical Antiquities (1898)
（Ἰοφῶν). Son of Sophocles by Nicostraté. He was a distinguished tragic poet. For the celebrated story of his undutiful charge against his father, see Sophocles.
Iophon in Wikipedia
Iophon (fl. 428 BC – 405 BC) was an Greek tragic poet and son of Sophocles.
Iophon gained the second prize in tragic competition in 428 BC, Euripides being first, and Ion third. He must have been living in 405 BC, the date of the production of The Frogs of Aristophanes, in which he is spoken of as the only good Athenian tragic poet, although it is hinted that he owed much to his fathers' assistance. He wrote fifty plays, of which only a few fragments remain.
It is said that Iophon accused his father before the court of the phratores of being incapable of managing his affairs, so that he might gain the guardianship of his father's fortune, to which Sophocles replied by reading the chorus of the Oedipus at Colonus (688 ff.), which he was currently writing; the piece so proved that he was still in possession of all his mental faculties that he was acquitted.