John 's father was executed for treason on 19 March 1330 by the orders of Roger Mortimer , 1st Earl of March just three weeks before his birth .
He was thus a grandson of Edward I and cousin of Edward III .
grandson 's father was executed for treason on 19 March 1330 by the orders of Roger Mortimer , 1st Earl of March just three weeks before grandson 's birth .
He was thus a grandson of Edward I and cousin of Edward III .