Kate Middleton's mom, Carole Middleton, was blamed for her trial separation with Prince William over a decade ago.

According to Jessica Jayne's book, "The Duchess of Cambridge: How Kate Middleton Became A Future Queen," the Duke and Duchess of Cambridge had a "trial separation" in 2004. The Sun's former royal editor Duncan Larcombe said he believes that the split had something to do with Carole.

In "William & Kate: The Journey," Larcombe revealed that Middleton's family background might have played a part. He added that there were members of the royal circle who used to cruelly poke fun at Prince William's wife behind her back.

"They used to say 'doors to manual' whenever they saw Kate Middleton," Larcombe said (via Express), which reportedly refers to Middleton's mother, Carole, who was a former airline hostess.

Larcombe added that while the palace vigorously denied that Middleton's background played a role, "one or two people in William’s inner circle may have that view."

Lucie Cave, editor of Heat Magazine, said she finds the Duke and Duchess of Cambridge's "separation" as something that makes them more relatable. In fact, the people saw them in a new light after that. "It made you realise that, actually, they are human beings," she said.

During their split, Prince William left Middleton furious when he decided to join Guy Pelly in an all-boys holiday trip. Middleton reportedly "never thought highly of" Pelly and even believed that he was a bad influence to the royal.

While the Duke of Cambridge was away, Middleton packed her bag and returned home to Berkshire to spend the summer with her family. She reportedly "let her guard down" around her friends.

"She got quite drunk on white wine and really let her guard down. She was debating whether or not she should text or call him," one of Middleton's friends said. "She said how sad she was and how much she was missing William but she never mentioned it after that."

Prince William and Middleton addressed their split during their engagement interview. "I think I at the time wasn't very happy about it, but actually it made me a stronger person," Middleton said about their split.

Prince William and Kate Middleton
Carole Middleton was blamed for Prince William and Kate Middleton's trial separation in 2004. Pictured: Middleton and Prince William laugh as they visit BBC Broadcasting House on Nov. 15, 2018 in London. Getty Images/Ben Stansall