The eldest son of Henry IV became king in 1413
[DOC] [TLE] King Henry IV of England - Wikipedia [PAR] Henry of Bolingbroke (15 April 1367  20 March 1413) /blbrk/, born at 
Bolingbroke ... His father, John of Gaunt, was the fourth son of Edward III and the 
third son to survive .... of his eldest son, Henry of Monmouth, who later became 
king (though the son managed to seize much effective power from his father in 
1410).