Morgawse
Morgawse was the eldest daughter of Igraine and Gorlois (Hoel), duke of Cornwall. This made her the half-sister of Arthur. She was the sister of Elaine and Morgan le Fay.
She was probably one and the same person as Anna, daughter of Uther and Igraine; therefore she was the full sister of Arthur in the early legend. All the authors said that Anna or Morgawse was married to King Lot and was the mother of Gawain. In the early legend, Anna only had two sons: Gawain and Mordred. In the later legend, she had four to five sons: Gawain, Agravain, Garheris and Gareth (or Gaheriet and Guerrehiet). Sometimes Mordred was mentioned as her son, sometimes he wasn't.
As early as the Vulgate Merlin, it was Arthur who was the father of Mordred, when Mordred betrayed him, implying that he had committed incest with Morgawse. However in the Suite du Merlin, the author was explicit; Arthur had unwittingly committed incest with Morgawse (see the Life of King Arthur). Since he was brought up by his foster-father, Sir Antor (Ector), he never knew that he had a sister. Mordred would grow up and betray his father, destroying Arthur and his knights. [This was also told in Malory's Le Morte d'Arthur: Vol. 1 Book 1 Chapter 19]
Morgawse also appeared as Norcadet with her mother (Igraine) in Chretien de Troyes' Story of the Grail (Le Conte du Graal), when Gawain appeared at the castle called Rock of Champguin. Although Gawain found out who they were, neither Morgawse nor Igraine could recognise him, since Morgawse had left him when he was still a child, about twenty years before.
Morgawse was pregnant with a daughter at the time of her disappearance. Gawain met his sister, who was called Clarissant.
Also in Malory's tale [Le Morte d'Arthur, Book X Chapter 24], Morgawse was still considered to be a great beauty. A knight named Lamorak was madly in love with Morgawse. When her son, Sir Gaheris, found her making love to Sir Lamorak, Gaheris was outraged that his mother was making love to his mortal enemy. Gaheris cut down his own mother's head with his sword. Gawain and his brothers were the mortal enemy of Lamorak, because Lamorak's father Pellinor had killed their own father (Lot).
By Jimmy Joe