James Middleton’s promise to his sister Catherine

James Middleton recently revealed the promise he made to his sister Catherine, Princess of Wales, while she was bravely battling illness.

In late June 2026, Kate Middleton , alongside her brother James, completed the grueling National Three Peaks Challenge ( a 37-kilometer route connecting the summits of Ben Nevis, Scafell Pike, and Snowdon) to raise funds for The Royal Marsden Cancer Charity, the charity associated with the hospital where she was treated. Her remission had been announced in January 2025, one year after her cancer diagnosis was revealed.

James Middleton shared his pride on Sunday, July 5, on Instagram, posting photos of the event alongside the princess, their parents, Prince William, and their three children. In the caption, he recalled the origins of this project, which began during a particularly difficult time: “Two years ago, I told you we’d climb this mountain together. We talked about climbing mountains while you were in the hospital, and about the incredible healing power that nature can have on both the body and the mind. So it was a tremendous honor to join you for your Three Peaks Challenge to benefit the Royal Marsden Cancer Charity."

The 39-year-old entrepreneur used this post to highlight and celebrate his older sister’s exceptional courage: “Seeing how far you’ve come is simply inspiring. Your strength, resilience, and determination—all while being an extraordinary mother, wife, daughter, and sister—inspire me and so many others every day.” Moved and grateful for this shared journey, he concluded his tribute with a tender declaration of affection: “Stay exactly as you are.”