EXCLUSIVE: Kate Middleton V Meghan Markle – New 'Moms War' Explodes As Kids Are Dragged into Vicious Feud

For anyone who's ever wanted to know more about how the Duke and Duchess of Sussex approached the 2021 birth of their second child, Lilibet Diana, now they know.

RadarOnline.com can reveal on June 4, Meghan Markle marked Lili's 4th birthday with three loving posts on Instagram – including a lengthy behind-the-scenes video filmed in her hospital room hours before the delivery.

Both Lili and brother Archie, 6, "were a week past their due dates," the 43-year-old captioned the clip, "so when spicy food, all that walking and acupuncture didn't work – there was only one thing left to do."

Meghan Markle twerked, bounced and dropped it down to Starrkeisha's The Baby Momma Dance song as Prince Harry dipped in and out of frame, showcasing his own moves.

The clip blew up on social media, where reactions were mixed, ranging from "joyful" and "relatable" to "cringey," "corny" and worse.

And the verdict back at Kensington Palace?

In-laws Prince William and Princess Kate "couldn't believe their eyes when they saw the video" – and it has led to a new ‘moms war" blowing up between Catherine and Markle.

"They thought it was so tacky and a very sad illustration of just how desperate and shameless the Sussexes have become with their attention-seeking behavior," a royal insider told RadarOnline.com, confirming that it's only widened the already deep divide between the couples and fueled tensions between the wives of the warring Mountbatten-Windsor brothers.

"Kate's privately told people that she wouldn't be caught dead acting in such a vulgar fashion," added the insider. "And it was incredibly galling for William to see his brother fooling around like a goofy teenager." Even with Harry, 40, in self-exile, he remains fifth in line to the throne "so it reflects badly on all of them."

The incident is just one of many recent moves by Markle that's rubbed the royals the wrong way.

Two days after sharing her delivery room twerking video, the former Suits actress followed up with another clip, this time showcasing her VIP visit to the Happiest Place on Earth with Prince Harry and their kids, accompanied by a gushing note of thanks to Disneyland "for giving our family two days of pure joy!"

Those followed Markle's June 3 social media announcement that both old and new products would be launching on her As Ever website, the same month.

It's all drawn accusations in the U.K. media that Markle – who's reportedly preparing to release a rosé wine in the coming weeks – has shifted from royal to run-of-the-mill influencer amid what's being seen as a barrage of self-promotion.

"Making money and building a brand is her mission and is important right now," a source close to the Sussexes told RadarOnline.com, explaining "ramping up her social media presence is crucial to achieving that goal."

But to some Sussex followers, it's sending a mixed message.

Markle, who vowed to continue her advocacy work for women when she and Harry stepped down from royal duties more than five years ago, for example, used to prioritize talk of changing the world. She traveled to Africa and beyond with a message of empowering women and girls.

Now she interviews multimillionaire girl bosses on her Confessions of a Female Founder podcast and offers what some critics have branded as out-of-touch entertaining tips on her Netflix entertaining series, With Love, Meghan, for people who have the time and money to tend organic gardens, arrange flowers and day drink with their wealthy pals.

It's a stark shift in her public persona from "feminist" to "flower sprinkles."

"She and Harry are insisting they're still just as committed to philanthropy and that more royal-style tours are in the works," said our Sussex source, noting that in 2024, the pair made successful jaunts to Nigeria and Colombia and remain active leaders at their charitable Archewell Foundation.

"But getting her business off the ground is also important."

Middleton, meanwhile, has – over the nearly 24 years she's known William – cultivated a rep that many consider above reproach.

A life of service and supporting charities is paramount to the future queen and has become a renewed priority since she returned to duty after recovering from a cancer diagnosis last year (and amid King Charles III's own battle with cancer).

"She is very conscious that she needs to conduct and carry herself in a manner that's becoming of a royal figure," said our royal insider.

Those same rules and principles extend to her and William's kids, Prince George, 11, Princess Charlotte, 10, and Prince Louis, 7.

"They are all being raised to understand they're held to higher behavioral standards," said the source. "It's as simple as that."

Now they're no longer working for the crown, Markle and Harry naturally have more freedom to set their own standards.

But when the duchess relaunched her Instagram account in January after years away from the platform, few expected her to start regularly sharing photos of Archie and Lili as she's now been doing for months.

"She sees no issue with putting them on social media, provided their faces aren't shown and that she and Harry are controlling the image," said the source close to the Sussexes.

However, the posts have raised eyebrows considering how protective they've been of their family.

Still, added the source: "Meghan knows that putting the kids online also gives her clicks."

It hasn't gone unnoticed back at the palace.

"For the royals, this is incredibly hypocritical," said our insider, pointing to Harry's recent confirmation his family has faced threats from neo-Nazis and the terror organization Al-Qaeda.

In May, after the army veteran learned he'd lost his years-long legal appeal concerning the denial of state-funded security for his immediate family in the U.K. – a decision he blamed on senior royals and palace courtiers.

Tthe palace has denied any involvement.

Harry told the BBC it's just not safe for Markle, Archie and Lili to visit the U.K.

"I think that it's really quite sad that I won't be able to show my children my homeland," he lamented.

To Markle's in-laws, it marked the moment the pair lost credibility.

"It's shocking the Sussexes have made this giant fuss over bringing their family to the U.K. and yet they still see fit to post highly personal photos all over social media," explained our insider. "It beggars belief and is a big reason why Kate's lost a lot of sympathy she used to have for Harry," amid his ongoing estrangement from William.

Though Middleton has remained silent publicly, privately, "it really upsets her that her children are also estranged from their cousins," said our royal insider.

They added: "It's unfair that these young, innocent members of the family are ultimately the victims in all this."

Right now, Markle is continuing full speed ahead.

Season 2 of her Netflix 'lifestyle' show will air in the months to come.

Her As Ever brand is restocking, her podcast has found an audience and just a few weeks ago she teased in a new interview with Fast Company she plans to explore the fashion category "at a later date, because I do think that's an interesting space."

All that ambition, however, could prove to be too much.

"It does seem to a lot of people that Meghan's jumping around a lot in terms of her priorities, and some are advising that it would be best to streamline things – that her image needs to be more focused," said our source close to the Sussexes.

They added: "But Meghan is very difficult to advise on anything. She's convinced she knows best."