Harry reportedly 'went ballistic' in moment that caused 'shift' in relationship with William

More alleged details of brothers Prince William and Prince Harry's reported falling out have come to light.

Various experts on the royal family shared their insights on the matter in a new documentary William & Harry: Princes at War, which mines Meghan Markle's introduction into the royal family and the various controversies that have arisen in her presence. It aired on Channel 5 on Sunday, August 18.

Carole Malone of Sky News said in the documentary that "the biggest cause of their so-called rift was Wills tried to warn Harry when he met Meghan not to rush into it."

"He'd only known her for less than a year when they got engaged," Malone explained. "He sat him down and just told him to take it a bit slow, not to run at it."

Harry and Meghan reportedly met through friends in the summer of 2016 and were engaged by the autumn of 2017. They wed in May 2018 and welcomed their first child together, Archie, in May 2019.

The Sun's royal correspondent Emily Andrews added that after being confronted by his older brother, Harry "went ballistic and said, 'You're trying to wreck this relationship before it's even started.'"

That being said, William and wife Kate Middleton were cautiously optimistic about the future Duke and Duchess of Sussex's relationship.

"It was all so quick that William and Kate didn't have a moment to get to know Meghan because Harry hardly knew Meghan," Ingrid Seward of Majesty magazine explained. "And, of course, quite naturally William and Kate would have thought, 'Oh, she's been married before, she's older than Harry, I hope she's going to make him happy.' Anyone would think that."

From Harry's perspective, however, his brother's inability to fully accept his relationship hurt, especially because "Harry supported William from the outset of his relationship with Kate," author Katie Nicholl said in the documentary.

"He felt very let down that he wasn't getting his brother's full 100 percent support with the relationship with Meghan," she added, noting that the confrontation was the moment "the dynamic changed" between the brothers.

"There was a shift and it was largely down to Harry resenting his brother," Nicholl added.

While the foursome reportedly get along much better now (parenthood has seemingly brought the Sussexes and the Cambridges closer together), they still did split in two major ways earlier this year: In addition to Harry and Meghan moving out of Kensington Palace, where Kate and William live with their three children, and into Frogmore Cottage at Windsor Castle, they also split off from the Royal Foundation to start their own charity.