It's long been reported that The Duchess of Cambridge and Meghan Markle have had a strained friendship since Prince Harry introduced the American actress to his family.
Insiders say the women didn't not get along, but instead, they were just "very different".
But it's also been claimed that Princess Charlotte "eased tensions" between the pair and helped them build up a bond.
In their unofficial biography Finding Freedom, Omid Scobie and Carolyn Durand claim that besides being married to brothers, the pair were never close.
Harry introduced his then girlfriend Meghan to his brother and Kate at Kensington Palace a few months into their relationship.
However, the book claims Meghan was left "disappointed" when she realised Kate was, as Scobie and Durand put it, " an extremely guarded person” with a tight-knit group of friends - which stopped the two women from getting friendly.
"Meghan would agree with the assessment that the duchesses were not the best of friends," the authors wrote.
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"Their relationship hadn’t progressed much since she was Harry's girlfriend.
"Meghan was disappointed that she and Kate hadn't bonded over the position they shared, but she wasn't losing sleep over it," the source added.
But it was Meghan’s “adoration” of Kate’s daughter Charlotte that diffused the tension between the pair.
During the early days of their relationship, Meghan lived with Harry at his Kensington Palace home, Nottingham Cottage.
With Harry and Meghan's place just around the corner from the Cambridges, Meghan spent a lot of time with Charlotte and her brothers George and Louis in the beginning.
This encouraged the Cambridges and Sussexes to put their differences aside when the kids were around.
Following this, Meghan gifted Kate a soft leather Smythson notebook which brought them together, and the pair later attended Wimbledon together two years in a row.
Speaking about the details in the book, Scobie told People: "A lot of damage has been done."
He also claims that Kate "barely acknowledged" Meghan during their final engagement as a four before the Sussexes quit the royal family.
The book also focuses on tensions between Harry and William which arose after the Duke of Cambridge angered the Duke of Sussex with comments about Meghan.
According to their sources, William said: "Don’t feel like you need to rush this" and "take as much time as you need to get to know this girl", reports People magazine.
They write: "Harry was p***ed off.
"P***ed off that his brother would ask such a thing. Some felt it was an overreaction.
"But then, this totally sums them up as people—William the calm and rational one, and Harry, who can’t help but take things far too personally."
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