Nephew, Then Son

Geoffrey of Monmouth's account of Mordred, the earliest full literary telling, makes him Arthur's nephew, the son of Arthur's sister Anna and King Lot of Orkney, a genealogy that gives Mordred a legitimate blood claim to stand as regent while Arthur campaigns abroad and makes his usurpation a betrayal of family trust rather than an outsider's naked ambition. That nephew relationship holds through several centuries of retelling before the developing prose tradition adds a far darker layer. The Vulgate Cycle, and Malory's English Le Morte Darthur following it, introduces an episode in which Arthur, not yet aware of his own parentage or hers, sleeps with his half sister, usually named Morgause in the English tradition, and conceives Mordred in that unwitting incest, so that the nephew of Geoffrey's account becomes, in this later strand, Arthur's own son as well. Malory has Merlin warn Arthur of a prophecy that a child born on May Day will one day destroy him, prompting Arthur to send every child born that day out to sea in a doomed attempt to drown the danger before it can grow, an act of attempted infanticide the infant Mordred alone survives, so that Arthur's own effort to escape the prophecy becomes, in the story's own logic, part of what guarantees it comes true.