Gareth is a Knight of the Round Table in Arthurian legend. He is the youngest son of King Lot and Queen Morgause, King Arthur's half-sister, thus making him Arthur's nephew, as well as brother to Gawain, Agravain and Gaheris, and either a brother or half-brother of Mordred. Gareth is particularly notable in Le Morte d'Arthur, where one of its eight books is named after and largely dedicated to him, and in which he is also known by his nickname Beaumains.

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.