King Charles III and daughter-in-law Princess Kate Middleton‘s simultaneous cancer battles have brought them closer than ever before.

“He has always had a very good bond with her. I don’t think it is presumptuous to say that she is like the daughter he never had,” royal biographer Sally Bedell Smith told People on Wednesday, March 27.

Charles, 75, ​shares the same desire as his son, Kate’s husband Prince William, to look after the princess after her “shock” cancer diagnosis.

“He shares with William an impulse to protect her. They are in this together, Kate and the King,” Sally added.

Buckingham Palace announced on February 5 that Charles had been diagnosed with cancer after it was picked up on a scan following a procedure for a benign enlarged prostate. The monarch immediately began treatment and noted in the statement that “He remains wholly positive about his treatment and looks forward to returning to full public duty as soon as possible.”

The king has been seen in photographs since his diagnosis attending church as well as greeting heads of state at Buckingham Palace.

Kate, 42, underwent major abdominal surgery on January 16, which at the time Kensington Palace said she would require 10 to 14 days in the hospital and enough time to recuperate at home that she wouldn’t be able to resume royal duties until “after Easter,” which is on March 31. The princess also wanted the nature of her operation to remain private.

Her long recovery period and public curiosity about her health crisis led to wild conspiracy theories about Kate’s whereabouts. She put rumors to rest in a heartbreaking announcement on March 22 that she had been diagnosed with cancer, sharing the news in a video while sitting alone on a bench in her garden.

Kate Middleton

Kate revealed that at the time of her procedure, “it was thought that my condition was non-cancerous. The surgery was successful. However, tests after the operation found cancer had been present. My medical team therefore advised that I should undergo a course of preventative chemotherapy and I am now in the early stages of that treatment.”

The princess said the diagnosis came as a “huge shock,” and “William and I have been doing everything we can to process and manage this privately for the sake of our young family.” The couple share three children, Prince George, 10, Princess Charlotte, 8, and Prince Louis, 5.

“As you can imagine, this has taken time. It has taken me time to recover from major surgery in order to start my treatment. But, most importantly, it has taken us time to explain everything to George, Charlotte and Louis in a way that is appropriate for them, and to reassure them that I am going to be OK,” she continued.

Kate did not disclose what type of cancer she was battling and made another plea for privacy. “We hope that you will understand that, as a family, we now need some time, space and privacy while I complete my treatment,” she told viewers.

A statement released by Buckingham Palace shortly after Kate’s video was released said, “His Majesty is so proud of Catherine for her courage in speaking as she did,” adding the monarch had been in “closest contact with his beloved daughter-in-law.”

King Charles and Queen Camilla said they would “continue to offer their love and support to the whole family through this difficult time.”

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