Complex sentence: John I, Duke of Cleves, Count of Mark (16 February 1419--5 September 1481) was son of Adolph I, Duke of Cleves and Mary of Burgundy.
Split into simpler sentences: John I, Duke of Cleves, Count of Mark (16 February 1419--5 September 1481) was Duke of Cleves and Count of Mark. He was the son of Adolph I, Duke of Cleves and Mary of Burgundy.