Prince Harry pushed his sister-in-law Kate Middleton to her “limits” with his bombshell BBC News interview last May, in which he discussed the health of his estranged father, King Charles III.

“The damage was done: seeds of doubt concerning the King’s chances for a full recovery had been sown,” royal expert Christopher Andersen writes in an excerpt from his upcoming novel, “Kate! The Courage, Grace, and Power of the Woman Who Will Be Queen,” obtained by Us Weekly.

During the shock interview Harry said he didn’t know “how much longer my father has,” which made Middleton “more disappointed than angry,” per the excerpt.

Prince Harry and Catherine, Duchess of Cambridge, attending a garden party at Buckingham Palace.
Prince Harry pushed his sister-in-law Kate Middleton (both seen above in 2017) to her “limits” with his bombshell BBC News interview last May.POOL/AFP via Getty Images

Prince Harry sitting on a couch during an interview.
Harry (pictured here during the BBC interview) discussed his estranged father’s health, saying at the time, “I don’t know how much longer my father has.”BBC News
“Princess Catherine is ‘the sweetest, most loving person you could ever know,’ said a Sandringham staffer, ‘but like everyone else, she has her limits,’” another of Andersen’s excerpt reads.

At the time, Harry, 41, was referring to his father’s cancer diagnosis in February 2024. In the years since, Charles has undergone cancer treatment and given positive updates on his health.

Andersen also told Us Weekly Harry’s interview really struck a nerve with Middleton, who went through her own cancer battle and really bonded with Charles, 77, because of it.

Catherine, Duchess of Cambridge, and Prince Harry attending a training day for the Heads Together team.
In his upcoming novel, “Kate! The Courage, Grace, and Power of the Woman Who Will Be Queen,” author Christopher Anderson claims that Harry’s comments made Middleton “more disappointed than angry.” (Middleton and Harry are pictured above in 2017.)UK Press via Getty Images

Catherine, Duchess of Cambridge, and Prince Harry at a Service of Hope at Westminster Abbey.
“Princess Catherine is ‘the sweetest, most loving person you could ever know,’ said a Sandringham staffer, ‘but like everyone else, she has her limits,’” Andersen’s writes. (Middleton and Harry are seen above in 2017.)Getty Images
“I think Kate’s relationship with her father-in-law over their shared cancer battles really has made her much more sensitive to King Charles’s feelings,” Andersen explained. “She knows better than anyone that having someone publicly imply you may be at death’s door is horribly demoralizing.”

“I’m sure Kate must have felt stung by that comment as well, since she is in a situation very similar to the king’s,” he added.

Anderson noted that Middleton, 44, has always been the “level-headed one” in the family feud and attempted to “bridge the widening gap between the brothers,” but Harry’s comments about Charles changed her stance. Afterward, she fully sided with her husband, Prince William, who was allegedly furious over his brother’s interview.

King Charles III and Catherine, Princess of Wales at the Requiem Mass service for the Duchess of Kent.
The comment especially hurt Middleton, as she and Charles (pictured above at Kensington Palace in 2025) bonded over their shared cancer battles, according to Andersen.GC Images

Catherine, Princess of Wales embracing King Charles III at a Requiem Mass.
“She knows better than anyone that having someone publicly imply you may be at death’s door is horribly demoralizing,” Anderson told Us Weekly. (Charles and Middleton are seen above in 2025.)Getty Images
“But William, who had already slammed the door shut on his brother over what Harry wrote in ‘Spare,’ was, in the words of a courtier, ‘apoplectic’ with rage,” he writes in an excerpt. “Now it was time to nail the door shut once and for all, and for the first time Kate, who had worked harder than anyone to mend the rift between the brothers, willingly handed her husband a hammer.”

Andersen told the outlet he doesn’t see Harry and Middleton “having any sort of relationship” going forward. “At least not for the foreseeable future,” he added.

Page Six has reached out to reps for Harry and Middleton for comment.

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Prince William, Catherine, Duchess of Cambridge, and Prince Harry at the Coach Core graduation ceremony.
The interview was also a turning point for Middleton as she stopped trying to “bridge the widening gap between” her husband, Prince Harry and his younger brother. (The trio are pictured above in 2017.)Getty Images

Catherine, Duchess of Cambridge, in a red suit and Prince Harry, in a blue blazer, arrive at the Global Academy.
Andersen told the outlet he doesn’t see Harry and Middleton (seen above in 2017) “having any sort of relationship” going forward.POOL/AFP via Getty Images
Harry has been on the outs with his father and older brother since he and his wife, Meghan Markle, resigned from their royal duties in January 2020.

The couple ultimately moved to Montecito, California, where they live with their two children: Prince Archie, 6, and Princess Lilibet, 4.

Harry went on to drag his royal family members in several interviews as well as in his 2023 memoir, “Spare.” However, the Invictus Games founder has since shared his desire to reconcile with the reigning monarch.

“Kate! The Courage, Grace, and Power of the Woman Who Will Be Queen” releases May 5.