According to a scholiast on Juvenal, Pegasus and his brother Griphus were named by their father after ships he commanded as a trierarch, or naval commander. Professor Edward Champlin of Princeton University provides evidence to show that ships of the imperial fleet were often named after swift and powerful winged beasts. He makes the suggestion that their father should be identified with a "M.Plotius Paulus qui et Zosimus", whose tombstone was recovered at Rome. An inscription from Dalmatia mentions him, but it is broken where it contains his name: [...]tius Pegasus. Champlin makes a convincing argument that the best restoration for his gentilicium is Plotius, the same as his brother.
There are some possible descendants of Pegasus or his brother. The cognomen of Lucius Plotius P[...], proconsul of Cyprus in 81/82, has been argued to be Pegasus, and thus the proconsul is very likely his son, although Ronald Syme has argued that the cognomen is actually Pulcher and is an otherwise unknown member of the Plautii Silvani.