Because Prince Hal is the heir to the throne, the King’s tense relationship with his son is almost inseparable from the matters of the kingdom. This links to the theme of succession and the legitimacy of rulership in the play, as the relationship between the two characters plays a big part in these aspects of the play. Because Henry IV, Part I is set amid a rebellion, the play is naturally concerned with the idea of rulership. The concept of legitimate rulership is deeply connected in the play with the concept of rebellion. Legitimate rulership can be said to be either due to the will of the people or to the will of God. Therefore, the doubt in the King’s power may result from his own fear that his rule is illegitimate since he stole the crown from Richard II.
Next in line for the throne after King Henry IV is Prince Henry, Hal, as he is the eldest of the king’s sons. The King often worries about Hal’s ability to govern after his death and also feels that Prince Hal was sent to earth by God as a form of punishment for him killing King Richard II and stealing the thrown. King Henry IV regularly exclaims that he wanted Hotspur was his son, saying he wishes:That some night-tripping fairy had exchangedIn cradle-clothes our children where they lay (Act 1, Scene 1, ll.86-87)According to King Henry IV, Hotspur would be a great king, which is the opposite of what he thinks of his own son, Hal. This allows Shakespeare to consider the similarities between kingship and parenting, with civil warfare being compared to a large-scale family dispute, which is an idea that is never lost in a play.
Moreover, King Henry IV’s relationship with his son demonstrates some issues surrounding primogeniture, the system in society which meant that the eldest sons in a family inherit their fathers’ titles, wealth, land, and therefore power. The play reminds us that, in this case, the civil war and the struggle for the crown is a family matter, and it highlights the struggles between fathers and sons, especially those who are royal.