The royal family determines who inherits the throne based on the British line of succession. When Queen Elizabeth dies, Prince Charles, being the one closest in line to the throne, will become the next king. In his death, his son, Prince William, will take his place. But what if Charles and Prince William die in a tragic accident? We know that Prince George, Prince William’s 5-year-old son, is the next in line. But can a child like him be in charge of the British monarchy? How old should he be before he becomes King?

If there is one royal protocol that the royals cannot break, it is the British line of succession. That means in the event that Prince Charles and Prince William die, Prince George will be hailed as the new king the millisecond his father passes away. And that is regardless of how young or old he is. When it comes to inheriting the crown, age is irrelevant.

The rules of the British line of succession state that there is no age limit for a monarch. That means that while the death of Prince Charles and Prince William won’t likely happen for many years, if it does, Prince George will become king. But there’s a catch: if he becomes king this young, he will not be able to ascend the throne until he reaches the age of 18, which is the eligible age for ruling. 

If George cannot use his power to rule until he is 18, who will rule the monarchy then? A regent. In the history of British monarchy, there was a time when Mary Queen of Scots became Queen when her father died. Since she was only six days old at the time, a regent was appointed to take care of the monarchy until she comes of age.

In the case of Prince George, Prince Harry is the most likely to become his appointed regent. According to the royal family’s Regency Act, the regent must be the person next in line to the throne who is at least 21 years of age. Although Prince Harry does not succeed Prince George of Cambridge in the line of succession, Princess Charlotte and Prince Louis are too young — even younger than George — so neither of them qualifies as a regent. Consequently, Prince Harry will have to make decisions on George’s behalf until all the duties of state finally fall on the young king’s shoulders at 18.

Prince George of Cambridge Britain's Prince George (C), accompanied by Britain's Prince William (L), Duke of Cambridge, arrives for his first day of school at Thomas's school. RICHARD POHLE/AFP/Getty Images