What little is known of Petro comes from Suetonius, who says that he was a native of Reate in Latium, and had been one of the loyal soldiers of Pompeius during the Civil War, and might have been a centurion.
He escaped capture after the final defeat of the Pompeians at the Battle of Pharsalus in 48 BC, and returned home, eventually receiving Caesar's pardon.
[1] Suetonius describes Petro's family as obscure, but he could find no evidence to support the claim that his father was from Cisalpine Gaul, and had contracted with the Umbrian and Sabine day laborers who worked the fields around Reate.
[4] Their son, Sabinus, followed his father's occupation, but suffered from ill health, and died in the country of the Helvetii around the end of Augustus' reign.
[1] Tertulla, who was still living, raised her grandson, the future emperor Vespasian, born in AD 9, on her estate at Cosa.