His father is Lot but there are uncertainties about his mother. Romancers finally settled on Morgause, Arthur's half-sister, making Mordred his brother or half brother. Undisputedly he has three more brothers- Gaheris, Agravain and Gareth. The Didot-Perceval gives him a sister, Elaine, as well. William of Malmesbury referred to him as early as 1125 as the nephew of Arthur. William also claimed that Gawain's tomb was found during the reign of William the Conqueror on the coast of Pembrokeshire. William says that Gawain fought against a brother of Hengist, the Saxon chieftain. Two accounts of his death are reported, both by ambush - one on board a ship where he is thrown overboard and the other at a banquet. Gawain has also been confused at times with the obscure St. Govan who has a chapel in the same county.
Except for his connection with Arthur, the tradition William draws on seems to fade away after the association with his uncle and the conflict with the first Saxon invasion in the mid-5th century. Geoffrey of Monmouth states that Gawain was educated in the papal household in Rome, distinguished himself with bravery in the service of Arthur and was slain in Mordred's rebellion.
Gawain is variously portrayed by poets and romancers. Oftimes, in English works especially, he is a chivalrous hero that endures and passes extreme tests like the one he undergoes in Sir Gawain and the Green Knight. Others, however, varyingly make him out as sometimes comic, a cheat and womanizer as well as vengefully violent. He nears attainment of the Grail but is denied due to his sins. He also embroils his brothers in a vendetta against Pellinore and his son, Lamorak. Pellinore had slain Lot whilst Gawain was but a child. Gawain's hatred of Lancelot extends, with fatal consequences, the dispute about the queen that splits the Round Table. He is wounded by Lancelot and dies at Dover. William Caxton, in the preface to his edition of Malory, tells the reader that Gawain's skull resides at Dover Castle and can still be seen.