Pereus belonged to the Elatid branch of the Arcadian kings, the house descended from Arcas. Apollodorus, naming the heirs who divided Arcadia among themselves, says that of them Elatus held all the power, and that he begat Stymphalus and Pereus by Laodice, daughter of Cinyras — so that Pereus stands as son of Elatus and brother of Stymphalus.2Pseudo-Apollodorus — Bibliotheca 3.9.1

Pausanias, charting the same succession, gives Elatus a fuller progeny: he reports that Elatus had five sons, Aepytus, Pereus, Cyllen, Ischys, and Stymphalus, setting Pereus second in the line. The brothers left their marks on the land — Cyllen on Mount Cyllene, Stymphalus on the spring and city of Stymphalus — while the death of Ischys, Pausanias notes, he had already recounted in his history of Argolis.3Pausanias — Description of Greece 8.4.4

Pereus left no son. Apollodorus traces his line through a daughter, Neaera, whom he gives in marriage to Aleus; from that union came Auge and the two sons Cepheus and Lycurgus, binding Pereus' blood into the Tegean house. Pausanias likewise records that Pereus had no male child but only a daughter, Neaera, yet he instead marries her to Autolycus of Parnassus — the two authors agreeing that Pereus' whole legacy ran through a single daughter, but parting over the man she wed.4Pseudo-Apollodorus · Pausanias — Apollodorus, Bibliotheca 3.9.1; Pausanias, Description of Greece 8.4.6