Passage 9.5.5
τὰ δὲ ἐφεξῆς μοι τοῦ λόγου προεδήλωσεν ἡ Σικυωνία συγγραφή, τοῦ τε Νυκτέως τὸν θάνατον, ὅντινα γένοιτο τρόπον, καὶ ὡς ἐς Λύκον ἀδελφὸν Νυκτέως ἥ τε ἐπιμέλεια τοῦ παιδὸς περιῆλθε καὶ ἡ Θηβαίων δυναστεία. Λύκος δὲ παρέδωκε μὲν αὐξηθέντι Λαβδάκῳ τὴν ἀρχήν· γενομένης δὲ οὐ μετὰ πολὺ καὶ τούτῳ τῆς τελευτῆς, ὁ δὲ ἐπετρόπευσεν αὖθις Λάιον Λαβδάκου παῖδα.
The subsequent portion of my account has been clarified for me by the Sicyonian chronicle, especially regarding the death of Nycteus, how precisely it occurred, and how the guardianship of the child and sovereignty over the Thebans passed to his brother Lycus. Lycus, indeed, entrusted the kingship to Labdacus once he had grown up; but when Labdacus also died not long afterwards, Lycus again became guardian, this time for Laius, son of Labdacus.