Edmund of Langley, 1st Duke of York

Edmund was born at Kings Langley Palace in Hertfordshire on 5 June 1341, the fourth surviving son of King Edward III and Philippa of Hainault. He became the 1st Duke of York and established the House of York, but the real leverage came a generation later: his younger son Richard of Conisburgh married Anne de Mortimer, great-granddaughter of Edmund's elder brother Lionel of Antwerp, Duke of Clarence. That marriage gave the Yorkists their claim to the English throne when the Wars of the Roses erupted. The Lancastrians they fought descended from another of Edmund's elder brothers - John of Gaunt, Edward III's third son. Edmund died on 1 August 1402, decades before the dynastic bloodbath his house would ignite.