The alleged conflict between Prince William and Princess Kate and the Duke and Duchess of Sussex has been well-documented. A new book by a royal family expert sheds further light on why problems began to arise between the two couples.

In his new book, "Catherine, the Princess of Wales: A Biography of the Future Queen," royal expert Robert Jobson discusses the events that led to the ongoing rift between the royal families. The Daily Mail. In an excerpt published by the Daily Mail, Robson writes "Initially, the public reaction to Meghan was overwhelmingly positive, with "the new kids on the block" dominating most headlines. There were even whispers of jealousy.

Once the trouble began, the relationship between the two royal couples began to fall apart. As Jobson explains, "With the help of petty insults, imaginary or otherwise, the cracks between the two couples continued to widen." Soon, the relationship seemed irreparable.

It is unclear whether Kate and William were actually jealous of Megan and Harry, but there was a definite change in their interactions with each other.

Jobson, an expert on the royal family, also revisited the infamous moment that allegedly occurred between Kate and Meghan, hinting at the discord. Jobson claims that "at one point, when Meghan asked to borrow some lip gloss, Harry felt that Lady Catherine had reluctantly given him her own." According to him, Lady Catherine "smirked" after Meghan put the lip gloss on her finger and applied it to her lips."

The "Harry and Meghan were not happy about it,"

Unfortunately, Prince Harry and Prince William, who once seemed to get along so well, suddenly found themselves at odds as well. Jobson writes, "Inevitably, leaks were made of the royal siblings' troubled relationship and the fact that Princess Catherine and Meghan were also at loggerheads."

Sadly, William and Harry's once close sibling bond has shown no signs of improvement in the years since; in a recent interview for the ITV documentary "Tabloids on Trial," Harry said that without adequate security, Meghan He stated that he believes it is still too dangerous for Meghan to return to the UK without adequate security.