In Greek mythology, Pergamus was the son of Neoptolemus and Andromache. Later Pergamene tradition held that he crossed to Asia Minor with his mother, slew the king of Teuthrania, renamed the capital Pergamon after himself, and ruled there — a foundation myth linking the Attalids to heroic ancestry. Distinct from Pergamus, the Homeric name for Troy's citadel.
Adapted from Wikipedia, "Pergamus" · CC BY-SA 4.0
I.Parentage
Pergamus's parents both figure in the Trojan War: Neoptolemus was Achilles' son and fought on the Greek side, while Andromache was Hector's wife. After the fall of Troy, Neoptolemus took the widowed Andromache as concubine and ruled in Epirus. After Neoptolemus' death, some sources say Andromache returned to Asia Minor with her youngest son Pergamus — probably a later addition to the legend.
II.Pergamon
The Kingdom of Pergamon seems to have created new mythology about Pergamus: upon traveling to Asia Minor with his mother, he killed the king of Teuthrania, renamed the capital Pergamum, and ruled as king. His line was said to include Attalus, forefather of the Attalid rulers. The account is widely read as a transparent link between the Attalids and Alexander's Epirote ancestry through Andromache; it was not a major strand of Attalid propaganda (unlike their Telephus claim), though at least one small heroon in Pergamon was dedicated to Pergamos Ktistes, probably in the third century BC.
III.Other uses
Pergamus (or Pergamos) is also Homer's name for the citadel of Troy, and the King James Bible uses "Pergamos" for the Asian city modern translations call Pergamum.