Diogenes Laertius, Lives of the Philosophers 3.1
“Plato was the son of Aristôn, an Athenian, and Periktionê, or Pôtônê, who alleged her heritage went back to Solon. For he had a brother named Drôpides who was the father of Kritias, the father of Kallaiskhros, the father of Kritias, who was one of the Thirty. He was also the father of Glaukôn, the father of Kharmides and Perictionê. Plato, then, as the son of Aristôn and that Perictionê, was the sixth generation after Solon. And Solon claimed his family descended from Neleus and Poseidon. They also claim that his father descends from Kodros the son of Melanthos and, they are said to descend from Poseidon, according to Thrasylos.
In his work named “The Feast for Plato” Speusippus writes, as Klearkhos claims in his Praise to Plato and Anaxlaides records in his second book of On Philosophers, that there was a story in Athens that Aristôn raped Perictionê when she was an adolescent girl and failed to get her [as a wife?]. When he stopped assaulting her, Apollo came to him in a dream. For this reason, he left her untouched of marriage until she gave birth.”
Πλάτων, Ἀρίστωνος καὶ Περικτιόνης—ἢ Πωτώνης,—Ἀθηναῖος, ἥτις τὸ γένος ἀνέφερεν εἰς Σόλωνα. τούτου γὰρ ἦν ἀδελφὸς Δρωπίδης, οὗ Κριτίας, οὗ Κάλλαισχρος, οὗ Κριτίας ὁ τῶν τριάκοντα καὶ Γλαύκων, οὗ Χαρμίδης καὶ Περικτιόνη, ἧς καὶ Ἀρίστωνος Πλάτων, ἕκτος ἀπὸ Σόλωνος. ὁ δὲ Σόλων εἰς Νηλέα καὶ Ποσειδῶνα ἀνέφερε τὸ γένος. φασὶ δὲ καὶ τὸν πατέρα αὐτοῦ ἀνάγειν εἰς Κόδρον τὸν Μελάνθου, οἵτινες ἀπὸ Ποσειδῶνος ἱστοροῦνται κατὰ Θρασύλον.
Σπεύσιππος δ᾿ ἐν τῷ ἐπιγραφομένῳ Πλάτωνος περιδείπνῳ καὶ Κλέαρχος ἐν τῷ Πλάτωνος ἐγκωμίῳ καὶ Ἀναξιλαΐδης ἐν τῷ δευτέρῳ Περὶ φιλοσόφων φασίν, ὡς Ἀθήνησιν ἦν λόγος, ὡραίαν οὖσαν τὴν Περικτιόνην βιάζεσθαι τὸν Ἀρίστωνα καὶ μὴ τυγχάνειν· παυόμενόν τε τῆς βίας ἰδεῖν τὴν τοῦ Ἀπόλλωνος ὄψιν· ὅθεν καθαρὰν γάμου φυλάξαι ἕως τῆς ἀποκυήσεως.