Kate Middleton and King Charles' diagnosis may have brought them closer, and it is evident in their recent public reunion, according to a royal expert.

The Princess of Wales made her first public outing at the monarch's annual birthday celebration to show her support for her father-in-law. The two royals, who announced their cancer diagnoses earlier this year, were seen standing next to each other when they appeared on the balcony to watch the flypast. One royal expert said their position on the balcony spoke volumes about their relationship.

"It's interesting," Emily Nash, royal editor at Hello! Magazine said on The Sun's "Royal Exclusive." "So I don't think it's particularly choreographed. But just the fact that they have naturally arranged themselves in that way."

Kate Middleton and Roya Family
(From L) Britain's Prince George of Wales, Britain's Prince Louis of Wales, Britain's Prince William, Prince of Wales, Britain's Princess Charlotte of Wales, Britain's Catherine, Princess of Wales, Britain's King Charles III and Britain's Queen Camilla stand on the balcony of Buckingham Palace after attending the King's Birthday Parade, "Trooping the Colour", in London, on June 15, 2024. JUSTIN TALLIS/AFP via Getty Images

She continued, "And the way they were chatting to each other is obviously a great deal of affection between them, that they have this shared experience now. We know that, you know, they spent some time together while we were both at the same hospital, and I think that while they were already quite close, this could only have brought them even closer together."

She added that Prince William's dad and wife standing next to each other on the balcony could have been a "tacit show of support" for each other. Nash also believes that His Majesty was "really happy" to see Middleton with them that day, especially since only the working royals joined the monarch on the balcony.

"There are fewer of them now, so they can move around a little bit more freely," Nash added. "In the days when there was 30 plus people on there [the balcony] then it was more of a question of where you are going to be wedged."

Royal family
Britain's Prince George of Wales, Britain's Prince William, Prince of Wales, Britain's Prince Louis of Wales, Britain's Catherine, Princess of Wales, Britain's Princess Charlotte of Wales, Britain's King Charles III and Britain's Queen Camilla wave on the balcony of Buckingham Palace after attending the King's Birthday Parade "Trooping the Colour" in London on June 15, 2024. HENRY NICHOLLS/AFP via Getty Images

The father- and daughter-in-law have since shared a close bond. His Majesty was the first to announce his cancer diagnosis, and Middleton also made a similar announcement months after she underwent abdominal surgery. King Charles, 75, reportedly traveled from London to have lunch with his "beloved daughter-in-law" when he heard about her condition, and he was "emotional" when they reunited.

King Charles has been supportive of Middleton for his older son, who is set to reign after him. When asked about Prince William and Middleton's engagement in 2010, he gave a light-hearted response.

"I'm thrilled. They have been practising long enough. It makes me feel very old," he said, per the Mirror.

King Charles, Kate Middleton and Prince William
Prince Charles, Prince William and Kate Middleton during a visit to Dumfries House on March 05, 2013 in Ayrshire, Scotland. Danny Lawson - WPA Pool/Getty Images

When Middleton was pregnant with Prince George, the Princess of Wales suffered from hyperemesis gravidarum, a form of acute morning sickness. His Majesty said when he spoke with journalists that he was glad she was getting better.

"It's a very nice thought of grandfatherhood in my old age, if I may say so. So, that's splendid. And I'm very glad that my daughter-in-law's getting better, thank goodness," King Charles said, per ABC News.

In October 2023, King Charles also called Middleton his "beloved daughter-in-law" when he delivered a speech at a state banquet held in his honor in Nairobi, Kenya.

"It was here, in sight of Mount Kenya, that my son, The Prince of Wales, proposed to his wife, now my beloved daughter-in-law," the King said, according to the Daily Mail.

King Charles also showed his support for Middleton when the latter announced her cancer diagnosis in March. Buckingham Palace released a statement saying, "His Majesty is so proud of Catherine for her courage and speaking as she did."

King Charles, Queen Camilla, Prince William and Kate Middleton
King Charles, Queen Camilla, Prince William and Kate Middleton during their visit to the Defence Medical Rehabilitation Centre (DMRC) in Loughborough, central England on February 11, 2020. RICHARD POHLE/POOL/AFP via Getty Images
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Kate Middleton, King Charles, Cancer