DRAMATIS PERSONAE
KING HENRY IV
PRINCE HAL – later King Henry V
PRINCE JOHN OF LANCASTER – Henry's son
DUKE OF GLOUCESTER – Henry's son
King Henry IV of England, (1367-1413). Though his family name was Plantagnet, he was widely referred to as Bolingbroke before taking the throne, after the castle near Spilsby in Lincolnshire where he was born. 
 
 A 16th century portrait of Henry IV, via  Wikimedia Commons. 
 King Henry  dies  towards the end of the play, leaving his son  Hal  to take the throne.
Henry IV Part 2 Characters of the Play