In all of the major literary sources, King Arthur Pendragon was fathered by Uther, or Uthr, has at least one sister and is married to Guinevere. He is a fictional character, and some aspects of his genealogy vary depending on the author of each story.
In the "Mabinogion," a collection of Welsh stories and one of the origins of the Arthurian legend, Arthur is fathered by Uthr Bendragon, and his mother is Eigyr. He has a sister, Gwyar. His wife is Gwenhwyvar and, they have three sons: Llacheu, Gwydre and Amhar.
The "Historia regum Britanniae" by Geoffrey of Monmouth has Uther as his father, Ygerne as the mother and Anna as his sister. This is the first spelling of his wife's name as "Guinevere," which remains fairly consistent through the other major literary sources, but the couple has no children in this version.
The romances of Chretien de Troyes spells Arthur's father's name as "Utherpendragon" and his mother's name as "Igerne." This version of the story introduces Morgan le Fay as Arthur's sister. In these stories, he has no children with Guinevere.
The Vulgate Cycle romances have Uther and Igerne, sometimes Ygraine, as Arthur's parents, and they add four sisters in addition to Morgan le Fay. Arthur's son is Loholt.
"Le Morte d'Arthur" by Sir Thomas Malory has Uther and Igraine as parents, Morgan le Fay and two others as sisters, and Borre as Arthur's son.