A royal writer says Prince Harry and Meghan Markle's active royal reign will end in January 2020, leaving a "charismatic vacancy" for Prince William and Kate Middleton's children to fill.

Cele Otness, co-author of Royal Fever: The British Monarchy in Consumer Culture (opens in new tab), is the author of Tina Brown's The Palace Papers (opens in new Borrowing the term "charismatic vacancy" from Tina Brown's "The Palace Papers" (opens in new tab), she says that since Harry and Meghan left office, that vacancy has persisted.

"There's a great quote from Tina [Brown] saying that one of the big problems with Harry and Meghan leaving the brand is that there is this 'charismatic vacancy,'" she told the Daily Express. 'I love that.'

For example, Otness says that before she died, Princess Diana filled the charismatic slot in the royal family. Now that Harry and Meghan are gone, "the position is filled by the Duke and Duchess of Cambridge's children, who regularly display their personalities," the Express writes.

Otness, a marketing professor who specializes in the royal family, says charisma is a necessary component of the royal family's brand image because it shows personality and appeals to audiences.

"What you want is for people to have personality, or at least for them to have that," she says.

And while Prince Charles "has more charisma than people give him credit for," Otness says he lacks confidence.

"What prevents him from expressing it is that he seems to be mired in self-pity and lack of confidence.

As for Princess Anne, Otness says, "She is not what one would call charismatic or caring."

But through visuals, not speeches, the Cambridges' three children, Prince George, 8, Princess Charlotte, 7, and Prince Louis, 4, can fill the void.

"Yes, it's William and Catherine's children that can do it, not through speeches, but through visuals," she said.

Who can forget Charlotte's cheeky remark outside Louis' christening in 2018? The then 3-year-old princess "showed she was a force to be reckoned with when she told the photographers, 'You're not coming,'" the Express wrote. Like Uncle Harry before her, Charlotte has also been spotted on numerous occasions sticking her tongue out at the crowd.

"She and her siblings have also not been able to help but look amused at 'Trooping the Colour' over the years, often being photographed with non-serious expressions on their faces," the magazine reported.

"As a child, Prince Harry was photographed many times sticking his tongue out at photographers.

The Cambridge children are certainly not lacking in personality, and it is a pleasure to watch them grow up with the occasional tongue out.