Sir Bors
Sir Bors the Younger is descended from Sir Bors the Elder, who reigned as king of Gaunnes (aka Gannis, Gaul) during the early period of King Arthur's reign. Sir Bors the Elder is the brother of King Ban of Benoic, who fathered Lancelot. He marries Evaine, the sister of Ban's wife, and begets Sir Bors the Younger and Lionel. Sir Bors the Elder teams up with King Ban and King Arthur to fight against the eleven rebel kings in Britain but both Bors and Ban are killed by Claudas. As a result, Bors' children are taken captive until the High Priestess of the Lady of the Lake rescues them and raises them alongside Lancelot. Eventually Sir Bors the Younger liberates Gaul from Claudas' reign and succeeds his dead father's throne.
Although he is a chaste knight, Sir Bors the Younger is bewitched into loving the daughter of King Brandegoris, who uses a magic ring to gain his affections. Through this union, Bors becomes the father of Elyan the White, who later becomes the Emperor of Constantinople. Nevertheless, his strict adherence to his celibacy vows contribute to his success in witnessing the Grail's mysteries firsthand.
~Fun Fact~
The painting on our Mysteries of the Grail homepage actually depicts Sir Bors and two other knights (Galahad and Perceval) as they finally achieve the Grail.