Prince William and Kate Middleton’s rumored feud with Prince Harry and Meghan Markle is real, according to a commentator.

Royal expert Anna Pasternak recently appeared on Yahoo’s ongoing series "The Royal Box," where she shared her thoughts about the fab four and said that the rumored rift between them is “undoubtedly true.”

The author of “Untitled: The Real Wallace Simpson, The Duchess of Windsor” also speculated on how Prince William feels about his sister-in-law. She believes the future king finds the Duchess of Sussex “difficult.”

“I think that Prince William is very responsible and as I said knows what his role is and Kate has come alongside that executed that extremely well and I think it's quite difficult to have had Meghan who have seems to want to modernise and set her own agenda and you can't have it all,” Pasternak said.

During the same interview, the author also warned Markle of her inappropriate behavior and encouraged her to follow Middleton and Camilla Parker Bowles' lead.

She commented that the two duchesses have adhered to the royal code by keeping quiet, not pushing their friends to the press and not pressing their case. Middleton and Camilla have kept it low-key while also working their way to where they are in the royal family, according to the royal commentator.

Pasternak said that Markle is in a “tricky situation” and reminded her that very little has changed in the monarchy in the last eight decades. She believes the spotlight will remain on Queen Elizabeth II and heir apparent Prince Charles and Prince William.

Prior to Prince William, Middleton, Markle and Prince Harry’s alleged falling out, there were rumors that the two brothers had a misunderstanding because the Duke of Sussex felt that his older brother was trying to destroy what he and Markle had. Prince Harry reportedly didn’t like it when Prince William told him that they didn’t know Markle’s background, intentions and what she really likes during their heart-to-heart talk.

Royal biographer Andrew Morton claimed that Prince Harry “went mental” after hearing that from the Duke of Cambridge. He added that the conversation really affected their relationship.

“He accused his brother of trying to finish his romance before it had begun. The brothers’ relationship has not really recovered,” he said.

Just recently, the palace announced that Prince Harry and Markle will be separating their household from Prince William and Middleton's. The Duke and Duchess of Sussex will be closer to the Queen as they will now be based at the Buckingham Palace.