Prince William and Kate Middleton are careful not to show public displays of affection during royal engagements – but behind palace doors, they are just like us.

The claim was made by royal author Tom Quinn in a new book titled "Gilded Youth: An Intimate History of Growing Up in the Royal Family." It features exclusive testimony from palace staff with historical sources, as well as royal insiders. It aims to examine the traditional upbringing of the British royal family and how it has impacted them over the years.

"Someone at the palace told me about the nicknames they have for each other," Quinn told Fox News Digital. "But it’s not all sweetness. They have terrible rows where they throw things at each other. Kate might seem to be a very calm person, and William also. But it’s not always true. Because the big stress for William and Kate is that they’re constantly surrounded by [palace aides]. It’s like a Jane Austen novel."

One former member of the palace staff who knew the Princess of Wales claimed to Quinn that Middleton, 41, refers to William, 40, as "babe," while he calls her "Duchess of Doolittle."

According to reports, William also calls his wife "Babykins" and "DoD," the shorter version of "Duchess of Doolittle." One report alleged that "Duchess of Doolittle" is a "gentle dig" after Middleton was previously criticized by Queen Elizabeth II for not having a full-time career before the couple married in 2011.

Allegedly, William fusses over Middleton’s "endless mane of hair" which prompts her to jokingly call him "baldy," according to one report.

One source claimed in the book that when William "is cross" with his wife, he’ll call her "darling" with "signs of annoyance" that can be detected in his tone.

KATE MIDDLETON WEARS CAMO GEAR AS SHE VISITS IRISH GUARDS WITH NEW HONORARY COLONEL TITLE

William previously admitted in a 2007 interview with NBC that his mother, Princess Diana, called him "Wombat," a name that has stuck with him into adulthood.

However, as quickly as they might argue, the couple will also "cozy up."

"Kate is very much the calm one," Quinn explained. "William is the one who’s a bit hotheaded. We see an example of that in Harry’s book… But Kate is very level-headed. She’s the one who will pour oil on troubled waters and go, ‘Let’s not stir things up.’"

In the book, the mother of three is described as having a "Buddhist calm."

"Of course, privately, William and Kate, like all couples, fall out, row, shout at each other and say unkind things to each other, but Kate is an appeaser by instinct and William always gives way as he had more than enough emotional turmoil, divorce and disruption as a child," wrote Quinn.

"He hates confrontation," Quinn added.

The couple first met while studying at the University of St Andrews. Their friendship turned romantic in 2002, and their relationship went public in 2004. They split in 2007 and got back together that same year. In 2010, William proposed, and the pair married the following year.

Quinn’s said Middleton’s stoic demeanor has been essential to her success in navigating the traditions of the British royal family.

CLICK HERE TO SIGN UP FOR THE ENTERTAINMENT NEWSLETTER

"I remember when the press was so horrible to Kate," he explained. "They said because her mother was a stewardess, as it used to be called in those days, no one would invite the family to any events where there was anyone of significance present. The press would remark how she was descended from working-class people, which is an absolutely cruel thing to say. But Kate never responded. She didn’t complain. She didn’t write letters to the press or ring in the editors. She said nothing. And that was a good move. She illustrated how calm she was about those things and didn’t make a fuss. And then, it vanished."

"Kate and Meghan [Markle] got the same nasty press coverage," he continued. "But in Meghan’s case, she complained that it was unfair, it was unkind, it was horrible. That only keeps the story alive for weeks. In Kate’s case, she ignored it. She’s very wise for it. And I think when she gets into any rows with William, she does the same – she just ignores it."

According to Quinn, it is known within the royal family that the Prince and Princess of Wales do not want to appear as "the perfect couple that everyone else should try and emulate."

"She said, ‘Like every other couple, we have days when we are really, really cross with each other, or days when we don’t talk to each other,’" said Quinn. "They want to be seen as an ordinary couple with the same stresses of having children, work and everything else that life brings."

One thing the couple has agreed on is how they want to raise their children, Quinn pointed out. Their eldest son Prince George, 9, is second in line to the throne.

"I think they are the first generation that you could almost say they’ve broken the mold of this very traditional royal upbringing where you basically pay other people to do all the work, and you only see your children for half an hour a day," said Quinn. "They’ve broken the mold, but not entirely. I think they like the idea that they’ve put out, that they want their children to have a more normal childhood because that goes down well with the public. On one hand, they want to represent this traditional continuity, this glorious world that the rest of us can look up to. But on the other hand, they want to be seen as ordinary people just like the rest of us."

PRINCE WILLIAM, KATE MIDDLETON'S WAX FIGURES TORN APART ONLINE: ‘SCARED ME’

"They’ve said they want their children to have a more normal childhood, and I think genuinely they will," Quinn shared. "But it won’t be as much as the rest of us. It won’t be in the same way that we define it. They’ve moved to Windsor, although they’ve kept their apartment at Kensington Palace. They moved to Windsor because there’s far more space for the children to play. But Eton, the prestigious school that the boys are more likely to go to, is only 10 minutes from Windsor. And that means their parents can see them more often. When poor [King] Charles was sent to school in Scotland, he didn’t see his parents for months at a time."

According to Quinn’s book, Middleton "wants to escape her middle-class childhood." She "dislikes burgers and chips and wouldn’t dream of taking her children to McDonald’s, and she doesn’t rock the boat when the vast weight of traditional royal pursuits bears down on their children." Quinn shared that she "was reduced to tears" on her first hunting outing with the royal family, "but she accepts that if the royals do it, then she must live with it."

A Buckingham Palace spokesperson did not immediately respond to Fox News Digital’s request for comment concerning Quinn’s book. However, a spokesperson previously told Fox News Digital that the palace does not generally comment "on such books."