Gaheris

Gaheris is a figure of Arthurian legend, a knight of the Round Table, and a son of Morgause and King Lot of Orkney and Lothian. His brothers are Gawain, Agravaine, Gareth and Mordred, a half-brother. His mother is a daughter of Gorlois and Igraine, and a sister of Elaine and Morgan le Fay. She is also an older maternal half-sister of King Arthur.
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[Arthurian] Gaheris is one of the sons of Morgause, Queen of Orkney. When he discovers Lamorak and Morgause in bed together he kills her but spares the unarmed Lamorak. He is banished by Arthur for the death of his mother. With another brother, Agravain, he later kills Lamorak in revenge. Gaheris was married to Lynette. He was killed by Lancelot during the rescue of Guinevere.