Kate Middleton seemingly took a subtle swipe at Prince Harry during a royal engagement following the publication of his explosive tell-all this week.

On Thursday, the Prince and Princess of Wales visited the Open Door Charity in Birkenhead, England, to learn how the organization uses creativity to inspire young people. Middleton and her husband Prince William met with four teenagers who were participating in the charity’s Oomoo program, which offers activities associated with the arts.

"Has producing music and taking part in those workshops helped?" asked the mother of three, as quoted by People magazine. "Has it helped you with your personal lives?"

"I’d say so," one young man replied. "For me, having that music as a tool is good for me to express my emotions through something I can enjoy. Producing music and letting out what you’re feeling is better than saying it in a clinical atmosphere. I can put it into words. That was tough to explain!"

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Prince William and Kate Middleton visiting the Open Door Charity

Prince William and Kate Middleton, the Prince and Princess of Wales, visit the Open Door Charity, a charity focused on supporting young adults with their mental health, using culture and creativity as the catalyst for change, in Birkenhead, England, on Thursday. (Jon Super-WPA Pool/Getty Images)

"Very articulate!" William, 40, replied.

"Talking therapies don’t work for some people, they’re not for everybody," Middleton, 41, replied. "It’s so important to have a range of therapies."

Middleton wasn’t the only royal who appeared to speak out amid the release of "Spare," which hit bookshelves Tuesday. Royal expert Hilary Fordwich told Fox News Digital that William responded "albeit off the cuff and extemporaneously" to an elderly woman in Liverpool. At the time, the couple was visiting Royal Liverpool University Hospital.

"[The woman] urged him to ‘keep going, keep going,'" said Fordwich. "Then I heard he responded, 'I will.' Now, I can’t promise this was in response to Harry’s accusations, but it sure sounds like it!"

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Kate Middleton listening attentively during a royal engagement

Middleton listens attentively during her visit to the Open Door Charity. (Jon Super-WPA Pool/Getty Images)

The outlet noted that mental health is one of the main areas of focus for the couple’s Royal Foundation, which was set up by William and Harry in 2009 before their wives joined following their marriages. Harry, 38, and his wife Meghan Markle, 41, left the Royal Foundation in June 2019.

Their Heads Together campaign also aimed to address the stigma of mental health and provide resources for those in need.

According to the outlet, William has used his platform to raise awareness of male suicides, as well as mental health support for medical workers. Middleton’s area of focus is mental health initiatives for children and young people. Her brother, James Middleton, has previously shared that his family, including the princess, joined him in therapy sessions when he was struggling with depression.

The Prince and Princess of Wales' social media, particularly Instagram, has put a spotlight on their royal engagements following the release of "Spare."

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Prince William and Kate Middleton visiting Liverpool

Prince William, Prince of Wales and Catherine, Princess of Wales visit the Royal Liverpool University Hospital in Liverpool, England, on Thursday. (Samir Hussein/WireImage)

In the ghostwritten memoir, the Duke of Sussex detailed his grief following the death of his mother, Princess Diana, as well as his strained relationship with the Prince of Wales. He also expressed his frustration at the role of royal "spare" in the shadow of his older brother, who is heir to the British throne.

Harry slammed the U.K.’s tabloid press for coverage he considered prurient, intrusive and sometimes plain wrong. He claimed his relatives were unwelcoming to his wife and even accused members of the royal family, including his stepmother Camilla, of leaking stories to the media to burnish their own reputations.

In the book, Harry detailed his long-standing sibling rivalry, which worsened after he began a relationship with Markle, a former American actress. The couple married in 2018. He claimed that during an argument in 2019, William called the former "Suits" star "difficult" and "rude," then grabbed him by the collar and knocked him down. Harry said he suffered cuts and bruises from landing on a dog bowl.

Harry also wrote about the time he notoriously wore a Nazi uniform to a costume party in 2005. He claimed that both William and Middleton encouraged the choice of outfit and "howled" with laughter when they saw it.

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Prince William, Kate Middleton and Prince Harry smiling during their Heads Together campaign

From left: Prince William, Kate Middleton and Prince Harry kick off their Heads Together campaign, which aimed to change the national conversation on mental wellbeing. The campaign took place in 2016. (Nicky J Sims/Getty Images for Royal Foundation)

Buckingham Palace officials have declined to comment on any of the allegations made in Harry's book. A spokesperson for King Charles III didn’t immediately respond to Fox News Digital’s request for comment. A spokesperson for Kensington Palace, which represents the Prince and Princess of Wales, told Fox News Digital it doesn’t have a comment. Allies of the royal family have pushed back on Harry’s claims, largely anonymously.

Harry’s exposure of bitter divides inside the House of Windsor — alongside details of his mental health struggles, experiences with sex and drugs and decadelong military career — has generated reams of media coverage. The father of two embarked on a press tour to promote the book, making appearances on ITV, CBS' "60 Minutes," ABC's "Good Morning America" and, most recently, CBS' "The Late Show with Stephen Colbert."

Harry told People magazine that therapy helped him cope with Diana’s death in 1997. The prince was 12 years old at the time of his mother’s sudden passing.

"Therapy also allowed me the space to address much of my trauma and grief by removing life’s filters — cleaning the windshield, and seeing life as it is, rather than through the fog," he explained. "The healing process has allowed me to get to a place where I now feel the presence of my mum more than ever before. She’s with me all the time — my guardian angel."

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Prince Harry Spare book

Prince Harry's book is already a top-seller. (Dan Kitwood/Getty Images)

The book gives no sign that royal family relations will be repaired soon. Harry told ITV that he wants reconciliation, but that there must be "accountability" first.

"Spare" is the latest in a string of public pronouncements by the Duke and Duchess of Sussex since they quit royal life in 2020. At the time, they cited what they saw as the media’s racist treatment of the duchess and a lack of support from the palace.

The Duke and Duchess of Sussex reside in Montecito, California, with their two children.

The Associated Press contributed to this report.