Edmund of Langley , 1st Duke of York ( 5 June 1341 â `` 1 August 1402 ) was a younger son of King Edward III of England and Philippa of Hainault . Edmund of Langley , 1st Duke of York , 1st Earl of Cambridge , KG ( 5 June 1341 -- 1 August 1402 ) was a younger son of King Edward III of England and Philippa of Hainault , the fourth of the five sons who lived to adulthood , of this Royal couple .