Beatrice and Eugenie 'to give Prince William their full backing' amid royal rift with Prince Harry

The royal couple also lived for a while at Frogmore Cottage, Prince Harry and Meghan Markle's former UK home, before the Sussexes were formally evicted from the property.

However, in May, the York sisters accompanied the Prince of Wales to a garden party at Buckingham Palace, in what was a strong show of solidarity between the cousins.

Princess Eugenie later wrote on Instagram: "Come rain or shine, I was delighted to support my family yesterday to meet some special individuals at the Buckingham Palace Garden Party who have gone above and beyond to support their local communities and the country."

This was viewed by many as a sign the mother-of-two had firmly shifted her alliance towards Prince William.

Beatrice and Eugenie were later seen laughing with Prince William and fellow cousin Zara Tindall at Royal Ascot in June.

At one point, William was photographed playing with the tassels on Eugenie's designer hat in a friendly encounter.

Royal commentator Richard Fitzwilliams claimed this was a signal that the York Princesses were supporting Prince William amid his feud with Prince Harry, 39.

He said: "With Catherine battling cancer, as she described so movingly in a statement released just before Trooping the Colour, Beatrice and Eugenie know it is a very difficult time indeed for the Royal Family."

Princess Kate admitted last month that her chemotherapy course would continue for a few more months and that she is "not out of the woods yet".

However, Kate, 42, is hoping to attend some engagements over the summer.

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Fitzwilliams added that Prince William's feud with his younger brother was on display when the Duke of Sussex did not meet any of his family members during his last trip to the UK in May.

He continued to tell The Mail: "Harry's last visit and the public confusion when he and his father did not meet, showed the depth of the rift.

"It would be of benefit to all if it were resolved, but until that happens Beatrice and Eugenie, who conceivably could act as go-betweens, are undoubtedly supporting William and are likely to give him their full backing if there are further attacks by the Sussexes on the Royal Family."