Lancelot was the son of King Ban of Benwick (Benoic, possibly Guenet in Brittany) and Queen Elaine (Ban's wife Elaine is the sister to King Bors' wife Evaine). His birth/baptismal name was Galahad, but was always called Lancelot, since his name was revealed in the cemetery of Dolorous Guard. According to the Grail legend, on his mother's side, Lancelot was the descendant of the line of King David of Israel.
He is known as Lancelot of the Lake or Lancelot du Lac because he was raised by the Lady of the Lake.
His illegitimate half-brother is Hector de Maris ( the natural son of King Ban of Benwick and the Lady de Maris)
King Bors is his uncle, and Sir Bors and Sir Lionel are his cousins.
Legend also says that Lancelot was the father of Galahad.
Sir Lancelot, knight of the Round Table