Bors belongs to the family at the centre of the French Lancelot-Grail romances. He is the son of King Bors the Elder and Evaine, the brother of Lionel, and the cousin of Lancelot. The distinction between father and son matters: the Grail knight is Bors the Younger, not the king whose name he shares. War with King Claudas deprives the family of its lands. The prose romances describe the boys' captivity and eventual rescue into the protection associated with the Lady of the Lake. Their early experiences place loyalty to family beside service to Arthur, a tension that follows Bors throughout his career.

The romances also make Bors the father of Elyan the White, known in Malory as Helin le Blank, by the daughter of King Brandegoris. Some prose versions explain their encounter through an enchanted ring. That episode should not be flattened into an uncomplicated account of freely chosen wrongdoing. The Grail narratives nevertheless interpret Bors through their medieval Christian ideals of chastity and repentance. A dream represents him as a white bull with a dark spot, distinguishing him from Galahad and Percival. His discipline during the quest includes religious counsel, restricted food and prayer, rather than simply a lifetime defined by tournaments.

His most painful test places two people in danger at once. Lionel is being beaten by two knights, while another knight is carrying off a maiden who calls for help. Unable to intervene in both directions, Bors chooses to save the maiden and entrusts his brother's safety to God. Lionel survives but treats that decision as betrayal. When they meet again, he attacks Bors, who initially refuses to fight his brother. A hermit and Calogrenant attempt to intervene and are killed. The confrontation is finally interrupted by a miraculous fire and a heavenly command, preventing the brothers from completing their violence against one another.

Other trials challenge Bors's ability to distinguish spiritual guidance from deception. A false religious counsellor tries to mislead him, while a woman threatens that she and her companions will die unless he yields to her demands. When Bors makes the sign of the cross, the apparent women are exposed as a demonic illusion. These episodes belong to the quest's religious framework: pity, obedience and loyalty are tested because appearances cannot be trusted. The narrative does not present victory in combat as sufficient preparation for the Holy Grail.

Bors eventually joins Galahad and Percival in the fulfilment of the Grail adventure at Corbenic and the journey to Sarras. Galahad dies after the final vision; Percival adopts a religious life and dies later. Bors survives and returns to Arthur's court, where the adventures are recorded. His distinction is being the returning witness among these three companions, not being the only person ever to see the Grail. Afterward he remains loyal to Lancelot during the conflict over Guinevere. Malory later places him among several surviving knights who enter religious life. Bors does not become Arthur's successor, and his survival should not be confused with the extinction of every other member of the Round Table.