Henry Percy's father and grandfather were killed in rebellions against what King of England who was also the Lord of Ireland from 1399-1413?
Henry Percy, 2nd Earl of Northumberland:  His father and grandfather were killed in different rebellions against Henry IV in 1403 and 1408 respectively, and the young Henry spent his minority in exile in Scotland. Henry IV of England: Henry IV (15 April 1367 – 20 March 1413), also known as Henry of Bolingbroke ( ), was King of England and Lord of Ireland from 1399 to 1413, and asserted the claim of his grandfather, Edward III, to the Kingdom of France.
Henry IV