Kate Middleton has become one of King Charles III’s most trusted family members, with royal watchers pointing to a shared cancer diagnosis and years of steady public service as factors that have deepened the bond between the king and the Princess of Wales.

Katie Nicholl, a royal correspondent for Vanity Fair and co-host of the podcast “The Royals Uncensored,” said the princess has consistently proven her value to the institution since marrying into the royal family. “I think Catherine, the Princess of Wales, has always been a very valuable asset to the royal family,” Nicholl told Fox News Digital. “She is the commoner who married into the royal family … [She has made] a seamless transition into that unique world of royalty. It’s not easy … There’s a huge amount of sacrifice that goes into being a member of the royal family.” Nicholl added that Kate has handled that sacrifice with composure. “Catherine’s had to give up a huge amount, and yet she does it all with a great deal of grace and dignity, always with a smile,” Nicholl said. “So she is absolutely the monarchy’s greatest asset.”

The relationship between Charles and Kate has grown notably closer following parallel health struggles both experienced beginning in 2024. Buckingham Palace announced the king’s cancer diagnosis that year, and Charles shared in December 2025 that his treatment would be scaled back in 2026. Kate revealed her own cancer diagnosis in March 2024, shortly after the king’s announcement became public. She completed chemotherapy that September and announced in January 2025 that she was in remission.

British broadcaster and photographer Helena Chard said the king has drawn inspiration from watching Kate navigate her illness. “King Charles sees enormous value in Princess Catherine,” Chard told Fox News Digital. “Not just as the wife of his heir, but as the cornerstone of the monarchy itself. He genuinely loves his ‘darling’ daughter-in-law. His face lights up when he is with her. They share similar interests, and they have shared a similar cancer journey, one that has created a deep bond and understanding that goes beyond duty.”

Chard said the late Queen Elizabeth II had recognized Kate’s value to the institution well before Charles ascended the throne. “The late queen saw it too,” Chard said. “She recognized Catherine’s superpowers early on — her ability to listen, find solutions and bring calm to difficult situations.” Chard also framed Kate’s role within Charles’s broader approach to his reign. “King Charles fundamentally views his time on the throne as stewardship,” she said. “He sees himself as the caretaker of the institution and is acutely conscious of preparing the next generation. Collaborative preparation between the king and his heir is essential. Having Princess Catherine as the wife of his heir, Charles has struck gold.”

Royal author Sally Bedell Smith, in previous comments to People magazine, described the relationship in more personal terms. “He has always had a very strong bond with her,” Smith told the outlet, adding that Kate is “like the daughter he never had.” Smith said Charles shares a protective instinct toward Kate with his son, Prince William. “He shares with William an impulse to protect her,” Smith said. “They are in this together, Kate and the king.”

When Kate’s diagnosis first became public, Buckingham Palace said Charles was “so proud of Catherine for her courage in speaking as he did.” Author Christopher Andersen has separately written that the king stood by Kate’s side during her treatment “to lend his cherished daughter-in-law moral support.”

Kate has continued advocacy work tied to her cancer experience in the time since her recovery, including a recent charity fundraising climb of the three highest peaks in the United Kingdom for the Royal Marsden hospital. Nicholl said that effort has strengthened public support for the princess. “Thankfully, despite a serious health issue, she has overcome that,” Nicholl said. “We’ve just seen her climb the three highest peaks in the United Kingdom to raise money for the Royal Marsden. She’s turning her experience into something positive, and I think that’s earned her a great deal of respect among the British public, along with a lot of love and affection. People are very much behind her and William.”

Chard echoed that sentiment, describing Kate’s broader connection with the public. “Princess Catherine connects with people in a way that restores faith in the monarchy,” Chard said. “She has learned every aspect of the institution over many years and has blended in carefully without fuss. Princess Catherine is central to the institution’s success, and King Charles knows this.”

Royal commentators say Kate’s steadiness has taken on added significance as the working royal family has grown smaller in recent years. Prince Andrew stepped back as a working royal in 2019 amid his ties to the late convicted sex offender Jeffrey Epstein, and Charles has since formally stripped him of his princely title and HRH style. Prince Harry and Meghan Markle, the Duke and Duchess of Sussex, stepped back from royal duties in 2020 and relocated to California.

Royals commentator Richard Fitzwilliams said the king’s appreciation for Kate extends to her partnership with William. “Naturally, King Charles recognizes the value of Kate, who is indeed the monarchy’s greatest asset,” Fitzwilliams told Fox News Digital. “We should add, ‘together with her partnership with William and their family.’ While we praise Catherine’s many strengths, William is the future king. She will one day be queen consort. They see themselves as a close-knit couple.” Fitzwilliams also pointed to Kate’s support for William amid reported tension over how to handle Harry. “William is currently at the center of reports that he and the king differ over how to handle Prince Harry, in particular,” Fitzwilliams said. “As she showed when the Sussexes met with the king and Queen Camilla, she fully supports William’s approach.”

Royals expert Hilary Fordwich said Kate’s steadiness has translated into measurable public goodwill. “It’s not at all surprising King Charles and Princess Catherine have bonded,” Fordwich told Fox News Digital. “One can tangibly feel the public also values her wonderful assets from the reception she always receives when in public, as well as in opinion polls. She has become indispensable and has won the public’s trust.” Fordwich attributed that trust in part to how Kate handled her illness. “She handled the strain of her cancer battle with dignity, without any indication of self-pity.”