Prince William and Kate Middleton started to speak to their eldest son, Prince George, about his birthright around his seventh birthday, according to a royal historian

George, who will be eight on July 22, will one day be the king of England following in the footsteps of his great-grandmother Queen Elizabeth II, grandfather Prince Charles, and father.

The Duke and Duchess of Cambridge reportedly wanted to delay talking to George about his "life of future royal service and duty" so he could have a "normal family upbringing."

In his new book, Robert Lacey claimed that William, 39, and Middleton, 39, wanted to make George aware that his life will be different from his other two siblings: Princess Charlotte, 5, and Prince Louis, 3. 

The royal biographer, who is also the official consultant on Netflix’s "The Crown," has updated his book "Battle of Brothers: William and Harry – The Inside Story of a Family in Tumult" with added chapters and new material. In the original book, which was published in 2020, the British historian addressed the ongoing woes impacted by the royal family.

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In 2020, royal expert and bestselling author Katie Nicholl spoke with U.K.'s OK! Magazine about how George is singled out. He often "gets taken away" from his sister and brother to participate in photoshoots with William, Charles, 72, and the queen, 95, per the U.K.'s DailyMail.

Kate Middleton and Prince William pose for a photo with their three children, George (right), Charlotte (middle) and Louis. 

Kate Middleton and Prince William pose for a photo with their three children, George (right), Charlotte (middle) and Louis.  (AP)

The idea of one day becoming a monarch is "being introduced to him gradually," Nicholl explained.

Despite the royal youngster's notably unique situation, Nicholl said that "the true enormity of what his life will one day be isn’t something he’s fully aware of yet."

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"I think George understands, like William did from a very early age, that he’s different from his younger brother and sister and that he’ll have a different future," she said. "After all, he gets taken away to do photoshoots with Her Majesty the Queen, so he must notice he’s been singled out."

Nicholl again stressed that William and Middleton treat the children equally, claiming the opposite was true for William and his younger brother Prince Harry.

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She claimed that as a child, William struggled to accept that he had "no choice about which path his life would take," so he's doing what he can to avoid putting a similar stressor on George.

Fox News' Nate Day contributed to this report.