King Arthur's family grew throughout the centuries with King Arthur's legend. Many of the legendary members of this mythical king's family became leading characters of mythical tales in their own right.

Gaheris is a Knight of the Round Table in the chivalric romance tradition of Arthurian legend. A nephew of King Arthur, Gaheris is the third son of Arthur's sister or half-sister Morgause and her husband Lot, King of Orkney and Lothian. He is the younger brother of Gawain and Agravain, the older brother of Gareth, and half-brother of Mordred. His figure may have been originally derived from that of a brother of Gawain in the early Welsh tradition, and then later split into a separate character of another brother, today best known as Gareth. German poetry also described him as Gawain's cousin instead of brother.