Gwrgi and Peredur are listed as sons of Eliffer (Old Welsh: "Elidir" or "Eleuther") "of the great warband" ("cascord maur") and as scions of the Coeling dynasty in the Harleian genealogies, making them first cousins of Urien. Likewise, a pedigree from Jesus College MS 20 includes Gwrgi and Peredur as brothers together with one Arthur "penuchel". Their principal claim to fame rests on their having fought in the Battle of Arfderydd. The "Annales Cambriae" report that this battle ("bellum Armterid") was fought in 573, but gives no further detail. A later expansion of the entry names Gwrgi and Peredur, both described as sons of Eliffer, as the chieftains on the victorious side and tells that Gwenddoleu ap Ceidio was defeated and slain in the battle. Under the year 580, the "Annales Cambriae" record the deaths of Gwrgi ("Guurci") and his brother Peredur ("Peretur"). These references give them a place as heroes in the Hen Ogledd of the late 6th century.