King Arthur was the son of Uther Pendragon and Igraine. Igraine was the wife to Duke Gorlois of Cornwall when she conceived Arthur. Through Merlin's magic, Uther was transformed to look exactly like her husband. Uther made love to Igraine. When Gorlois was killed, Uther immediately married Igraine.
According to Geoffrey, Uther and Igraine were parents of King Arthur and a daughter named Anna, who married King Lot of Orkney. Chretien de Troyes' introduces Morgan le Fay as the sister of King Arthur.
In Gerald of Wales Tour of Wales (1188), he has Morgan as Arthur's cousin.
Malory credits King Arthur with three half-sisters: Morgawse, Elaine (Blasine) and Morgan le Fay. Morgawse had married King Lot of Orkney, Elaine (Blasine) was married to King Nentres of Garlot, and Morgan was wife of King Urien of Gorre, brother of Lot.
Most souces do not ascribe any children to King Arthur and his wife Guinevere. But Chretien de Troyes' gives a son Lohot (or Loholt) fathered by King Arthur, but the mother being Lisanor. Lohot was one of the Knights of the Round Table. Lohot was also one of the knights captured by the lord of Dolorous Guard.
Malory, gives a son was named Borre to King Arthur with the mother named as Lionors. The similarity between the two women's names - Lisanor and Lionor, suggested that Lohot and Borre is the same person.
In Culhwch and Olwen (c. 1100), King Arthur was the father of Gwydre, possibly by Gwenhwyvar (Guinevere). Gwydre was killed by a wild boar. In the Welsh romance "Gereint and Enid", the story mentioned that King Arthur had a son named Amhar.
His most noteworthy "son" was Mordred. In the early chronicles like Geoffrey of Monmouth, Mordred was Arthur's nephew, because Mordred was the son of King Lot and Anna or Morgawse, the sister of Arthur. But by the Vulgate version, it was implied that Mordred was his son by Arthur's half-sister, Morgawse. In the Suite du Merlin Arthur had unwittingly slept with Morgawse, because he did not know that she was his half-sister. Some say that Morgan le Fay was Mordred's mother.
| Mabinogion &
other Welsh sources
|Uthr Bendragon||Eigyr||Gwyar||Gwenhwyfar or Gwenhwyvar||Llacheu, Gwydre, Amhar|
| Historia regum Britanniae
Geoffrey of Monmouth
|Chretien de Troyes' romances||Utherpendragon||Igerne||Morgan le Fay||Guinevere||–|
|Vulgate Cycle romances||Uther||Ygraine or Igerne||Morgawse, Blasine, Brimesent, unnamed, Morgan le Fay||Guenevere||Loholt (by Lisanor)|
| Le Morte d'Arthur
Sir Thomas Malory
|Uther||Igraine||Morgause, Elaine, Morgan le Fay||Guenivere||Borre (by Lionors)|
There is a reasonable agreement on the genealogy of King Arthur across most sources. Certainly King Arthur had a colourful family history.
The Legend of King Arthur