The Princess of Wales has long enjoyed a friendship with her husband's cousin, Zara Tindall.
The pair have exchanged hugs at the Royal Ascot and Kate has even appeared on her husband's podcast - however, the same warmth doesn't appear to extend to his disgraced Uncle Andrew Mountbatten's daughter Beatrice.
It is perhaps no wonder that cautious Catherine - who will one day be Queen - could be keeping her distance from the royal wild child, who in the noughties made headlines for everything from her slew of boyfriends 'hated' by the Prince of Wales to raucous parties with her mother Sarah Ferguson.
Beatrice was just 17 when she started dating the late Paolo Liuzzo, a 'troubled playboy' seven years her senior.
After meeting through friends and getting together in July 2005, the young royal was reportedly partying up a storm with the Italian-American magnate and her mother just two weeks into the romance.
As revealed by historian Andrew Lownie, in his new book Entitled, during that time the then-Duchess of York was enjoying an 'annual two-week stay at Paddy McNally's villa in the South of France'.
She and her family 'were joined by twenty-three-year-old Paolo Liuzzo, her teenage daughter Beatrice's new boyfriend, whom she had met a fortnight before'.
While Liuzzo had a 'chequered' past - he had been charged with manslaughter during his time at university in Massachusetts after a drunken fight led to the death of a teenager - he was still, it seems, welcomed into the royal fold by Sarah and Andrew.
A history of raised eyebrows from the late Queen is likely to have unnerved Kate - whose husband is also understood to have been distancing himself from the Yorks.
Lownie continued: 'Driving from Geneva, he brought with him some friends who proceeded to have a good time - Liuzzo spent thirty thousand euros one evening entertaining the party at Club 55 in Saint-Tropez.
'The duchess then invited him to join her and her two daughters a month later - taking a holiday at Richard Branson's safari ranch in South Africa in between - at Round Hill, an exclusive resort of villas, in Jamaica.
'Liuzzo later sold an account of his two trips to a newspaper, claiming the duchess had encouraged his relationship with Beatrice and exposed her daughter to people who took drugs, including cannabis, much to the Queen’s concern.'
Such a history of raised eyebrows from the late Queen is likely to have unnerved Kate - whose husband is also understood to have been distancing himself from the Yorks.
Her Majesty's disapproval, it seems, only continued to grow as 'Liuzzo was proving to be trouble'.
In November 2005, Lownie revealed that one of Sarah's 'property developer friends' had 'lent him her seven-floor mansion' in Belgravia - and had to splash out £7,000 to clean up the aftermath of his hedonistic 'raves'.
Supportive Sarah, who had established herself as Liuzzo's 'second mother', vouched for her teenage daughter's boyfriend, but in May 2006, 'on the orders of the Queen, Beatrice ended the relationship'.
Liuzzo also later alleged that he lent Andrew $10,000 - which was 'never fully settled'.
According to Lownie, this was to 'pay for removal men to move one of the duke's girlfriends, Angie Everhart, out of the New York apartment she shared with her then fiancée'.
Liuzzo was later allegedly 'asked to kneel in the drawing room of their Windsor mansion for a mock knighting ceremony' as 'impersonating the queen, the Duchess of York handed him a new nickname: "Sir Fixit"'.
After the break-up Liuzzo divulged a myriad of information about the royal family, including claims that every New Year Andrew went through a ten-day ritual featuring 'cleansing' massages and that the disgraced Duke had asked PPOs to shoot squirrels at Royal Lodge.
He also said that Beatrice claimed of her parents: 'Daddy loves Mummy more than Mummy loves Daddy. But Mummy lives for her title and she loses her title if Daddy remarries.'
'Liuzzo also said the duchess authorised him to use the Yorks' businessclass-only airway, EOS, which had just launched and gave them free flights,' Lownie added. 'Telling him when he needed a flight, "Talk to my assistant and they'll sort it out."'
The following year, it was time for Beatrice’s 18th birthday party - ‘a lavish costume ball at Windsor Castle for five hundred, with dinner for 250 earlier, reputed to have cost £400,000’.
However, key members of the Firm - namely the Queen, Charles, Camilla and William and Harry - did not attend.
Those present, however, included Jeffrey Epstein, Ghislaine Maxwell and Harvey Weinstein. It also featured a £10,000 dress designed by Marchesa, the New York fashion house established by Georgina Chapman, wife of Harvey Weinstein.
It wasn't the only of Beatrice's parties with controversial characters. At her 21st, in 2009, convicted Libyan gun smuggler Tarek Kaituni gifted her an £18,000 diamond necklace.
William also appears to have a history of tensions with Beatrice’s partners, which goes way back - as the prince reportedly ‘hated’ her ex-boyfriend of ten years, Dave Clarke; despite being the one to introduce them.
The royal knew American businessman Dave from St Andrew’s University and introduced him to Beatrice at a 2006 party held by Pierce Brosnan’s son Sean.
However, in 2011, it appeared all was not smooth sailing when William and Kate left Dave off the invite list for their wedding.
The reason for the souring, a source told the Daily Mail, was allegedly Dave’s ‘indiscreetness’.
‘William has the Spencer paranoia gene,’ an insider shared.
‘Dave is a gregarious, chatty American and William is so private it hurts. He would accuse his dog of being indiscreet if it barked at someone else too often.’
Another shared: ‘William isn’t a huge fan of Dave. It’s fair to say that if Beatrice had asked the Queen for permission to marry Dave, and she in turn asked William privately for his view, she may not have been given a glowing report.’
Commentator Richard Fitzwilliams shared that it seems the Prince also found him ‘unreliable’.
The couple split up in 2016, and two years later, in 2018, she reportedly began dating longtime family friend Edoardo Mapelli Mozzi, who she has been married to since 2020.
Since controversy about Beatrice and Eugenie's parents continued to erupt in recent years, experts have suggested the Princess of Wales and her husband are likely to want to distance himself from the York sisters.
Elsewhere, Beatrice showed 'awkwardness and dislike' towards William and Kate following the Christmas Day service at Sandringham, a body language expert has recently claimed.
She had accompanied members of the Royal Family for the traditional walkabout and service at St Magdalene Church.
While others, including Zara and Mike Tindall, were seen happily chatting to William and Kate, Beatrice’s display was, according to UK body language judge Judi James, on the ‘awkward’ side.
It comes after Princesses Beatrice and Eugenie were told they cannot join their family at Royal Ascot this year amid concerns about the escalating scandal involving the House of York and their ties to Jeffrey Epstein.
Sources say the sisters, whose names appear several times in the Epstein files, will not take their seats in the Royal Box at the prestigious horse-racing event in June, nor can they join senior royals for the Royal Procession.
The move is said to have 'completely blindsided' Beatrice, 37, and Eugenie, 35, who are already reeling from the arrest of their father last month on suspicion of misconduct in public office.
But perhaps signs of the York sisters' growing distance from William and Kate were evident long before news of Ascot.
Speaking to the Daily Mail about Beatrice's Christmas Day appearance, Judi said: 'There is a type of smile known as a performed or applied rictus that is a wide smile that appears effortful and not prompted by authentic pleasure.
'Often the wider the smile, the more negative the emotions being masked, which could be why Beatrice’s smile here, as she waits for the Waleses to go first, hints at what could be awkwardness or dislike.
'She begins in something of a huddle with her sister, where the smiles could suggest some conversation through gritted teeth as they watch William, Kate and the children take the lead.
'The sisters seem to decide to shuffle off together to the left, where they stand beaming their smiles at the group in front in a watchful rather than sociable way.
'Beatrice’s glance down at the Waleses hints at some quiet impatience or discomfort at having to hang around dutifully and compliantly until they move on.
'There is no sign of any socialising between them here or any intent of catching Kate’s eye to make the smiles more sociably friendly.'
The decision followed a claim from royal commentator Richard Fitzwilliams that William and Kate 'won't' miss the York sisters if the future King has to 'take the hard line' with his cousins.
Their relationship has long been strained, but the latest revelations from the Epstein files could cause it to deteriorate further.
The most recent tranche of Epstein documents has raised serious questions about how much the former Duke and Duchess of York's daughters knew of their parents' corrupt dealings with the paedophile financier.
One email sent by Epstein in 2015 - after he was convicted for soliciting sex from a girl under 18 - boasted to a friend that Beatrice 'liked' him.
It also emerged that Beatrice helped advise her mother on how to placate Epstein after Fergie called him a paedophile while apologising for accepting a £15,000 bailout from the convicted sex offender in a 2011 interview. She also played a key role in facilitating her father's 2019 Newsnight interview.
William must now evaluate his relationship with Beatrice and Eugenie and assess whether they have a future within The Firm - a decision which will no doubt be fuelled by the pre-existing tension in his relationship with the York sisters.
'It may fall to William to make a decision on the future of Beatrice and Eugenie. Neither are reportedly particularly close to him or to Catherine,' Richard added.
'The fact that Beatrice, when 20, and Eugenie, aged 19, visited Epstein in Florida just after his release from prison with their rapacious mother is alarming. They must have known who they were visiting and how inappropriate this was. He was under house arrest.'
'One of the most bizarre aspects of the files is the way Sarah Ferguson seems to regard Epstein as part of her extended family. In 2010, she even told Epstein of Eugenie’s “s*” weekend.'
'There is obvious sympathy for the predicament of the sisters; mention in the files does not denote wrongdoing.'
'The King reportedly regards their work-life balance where they both do some charitable work alongside their careers and families but are not working royals as admirable.'
'William it is reported may well take a hard line when he becomes King. It depends on how affected the Royal Family is by what happens subsequently.'
'If this happens it may be impossible for the Royal Family to move forward with any members of the York family attached to it.'
'William and Catherine do not appear to have close ties with the sisters and would probably not miss them.'
Richard added: 'Although the Waleses may not be close to the sisters we know that Eugenie is notably close to Harry.'
'At one time it was thought that she had a role to play in helping reconciliation between the Royal Family and the Sussexes. That is now highly unlikely.'