Who is the mother of King Arthur's son?

Answer 1

Sir Mordred was the son of Morgause (also known as Anna). Morgause was the half-sister of Arthur, having been the daughter of Gorlois, Duke of Cornwall and Igraine (whom Uther Pendragon took for his own after defeating Gorlois). It is speculated in some writings that Morgause and Arthur were not aware of their relationship at the time of Mordred's conceiving. As with all Arthurian legends there are numerous different interpretations of the story.