Prince William, Kate Middleton told Prince George he was going to be King around his 7th birthday

Prince William and Kate Middleton informed their eldest son, Prince George, around his seventh birthday about the huge responsibility of the British throne that lies in his future.

Prince George, great-grandchild of Queen Elizabeth II, is third in the line of succession to the British throne after his grandfather Prince Charles and father Prince William. Royal author Robert Lacey claims that William and Kate held off on discussing George's future role as King of England in his early years to give him a "normal family upbringing."

The Duke and Duchess of Cambridge wanted to reveal it to George at a "controlled moment of their choice." They finally discussed the "life of future royal service and duty" that lies ahead of him "sometime around his seventh birthday," which he celebrated on July 22nd last year.

"William has not revealed to the world how and when he broke the big news to his son. Maybe one day George will tell us the story himself. But sometime around the boy's seventh birthday in the summer of 2020, it is thought that his parents went into more detail about what the little prince's life of future royal 'service and duty' would particularly involve," Lacey writes in a new chapter of his updated book "Battle of Brothers," reports Mail Online.

"William's aim as a father, the prince stressed, was to give his son 'a normal family upbringing,' enabling the monarchy 'to stay relevant and keep up with modern times,'" Lacey added.

The royal biographer noted that William and Kate's decision to wait till George's 7th birthday was influenced by the Duke's own experiences, and reflected his "unhappiness at the haphazard fashion in which the whole business of his royal destiny had buzzed around his head from the start."

Lacey also discussed the portrait of the present and future monarchs of the United Kingdom clicked in the throne room in December 2019 and released in January last year. If George came to know about his future as a King in July last year, it means that he did not know the significance of the picture when he posed with his father, grandfather, and great-grandmother.

"The prince had been placed on a rep-carpeted step in order to bring him up closer to the level of his great-grandmother. What a fascinating and historic image to remind us of the essence of the royal system! The current monarch with three future monarchs. All the living heirs - and not a suggestion of a "spare," Lacey wrote.

According to sources, the throne room portrait was the idea of Prince Charles, who wanted it to promote his plans of a "slimmed-down monarchy." It is widely speculated that the heir apparent will remove many senior royals from their positions when he takes over the throne from his mother, as he believes the public does not want to pay for a huge and ever-growing monarchy. His heir Prince William and the latter's children Prince George, Princess Charlotte, and Prince Louis are expected to be a part of the monarchy when they come of age.

A royal expert claimed last year that George knows he is "very different" from his two siblings despite their parents' numerous efforts to treat their children as equals. Katie Nicholl said that William and Kate aren't raising George to be spoilt or get special treatment, but he has noticed that he is often "singled out" to spend time with the Queen and Prince Charles.