Passage 1.13.4
ἑτοιμοτέρῳ καὶ ἄλλως ὄντι ἑλέσθαι τὰ ἐν χερσίν. Κλεώνυμος δὲ οὗτος, ὁ τὸν Πύρρον ἀπολιπόντα τὰ Μακεδόνων πείσας ἐς Πελοπόννησον ἐλθεῖν, Λακεδαιμόνιος ὢν Λακεδαιμονίοις στρατὸν ἐς τὴν χώραν πολέμιον ἐπῆγε διʼ αἰτίαν, ἣν ἐγὼ τοῦ γένους ὕστερον τοῦ Κλεωνύμου δηλώσω. Παυσανίου τοῦ περὶ Πλάταιαν τοῖς Ἕλλησιν ἡγησαμένου Πλειστοάναξ υἱὸς ἐγένετο, τοῦ δὲ Παυσανίας, τοῦ δὲ Κλεόμβροτος, ὃς ἐναντία Ἐπαμινώνδᾳ καὶ Θηβαίοις μαχόμενος ἀπέθανεν ἐν Λέκτροις· Κλεομβρότου δὲ Ἀγησίπολις ἦν καὶ Κλεομένης, Ἀγησιπόλιδος δὲ ἄπαιδος τελευτήσαντος Κλεομένης τὴν βασιλείαν ἔσχε.
He was in any case the more ready to take what lay easily within his grasp. This Cleonymus, who persuaded Pyrrhus to leave Macedonian affairs behind and come to the Peloponnese, being himself a Lacedaemonian, brought an enemy army against the Lacedaemonians into their own land, for a reason which I shall explain when I later speak of Cleonymus's family. Pleistoanax was the son of that Pausanias who had led the Greeks at Plataea; Pausanias was the son of Cleombrotus, who fell fighting against Epaminondas and the Thebans at Leuctra. Cleombrotus had two sons, Agesipolis and Cleomenes. Agesipolis died childless, so Cleomenes inherited the kingship.