YORK , Richard Plantagenet, duke of, son of Richard, earl of Cambridge, and relentless leader of the Yorkist cause in Shakespeare's Henry VI, Part 1 , Henry VI, Part 2 , and Henry VI, Part 3 . York, a cunning politician and formidable soldier, is convinced that he is the rightful heir to the throne. To achieve this end, he instigates the conflict known as the Wars of the Roses and secretly encourages Jack Cade's insurrection. York is followed in his quest by his sons, Edward, earl of March (later Edward IV), Richard, duke of Gloucester (later Richard III), and George, duke of Clarence.