Princess Kate's brother supports Catherine for bold step

James Middleton has sent an emotional message to his sister Princess Kate after her unexpected move.

James celebrated the Princess of Wales remarkable accomplishment on social media

James, himself a keen hiker, responded to Kate's Instagram video explaining her motivation with a simple but powerful message: "So proud."

Beneath a photograph showing the Princess radiating joy after finishing , Three Peaks Challenge, James added a subtle yet meaningful tribute, a mountain emoji paired with a heart.

Catherine's took a bold step just 18 months after she revealed her cancerdiagnosis following a planned abdominal surgery.

James, had previously posted a childhood photograph of the siblings on a mountain walk, writing: "Over the years, we have climbed many mountains together. As a family, we will climb this one with you too."

The Princess covered an extraordinary 23 miles on foot this weekend, ascending more than 10,000 feet across Britain's three highest peaks, with 462 miles of driving between each mountain.

Her route took her up Ben Nevis in Scotland at 4,413 feet, Scafell Pike in England at 3,209 feet, and Snowdon — known as Yr Wyddfa — in Wales at 3,560 feet.

Catherine undertook the challenge alone, with Mountain Rescue providing support throughout the demanding route.

The achievement is believed to be a royal first, with no other member of the Royal Family having previously conquered the National Three Peaks Challenge.

On Sunday, the mother-of-three shared her deeply personal motivation for undertaking the gruelling physical test, describing it as an opportunity to highlight life beyond a cancer diagnosis.

"The Royal Marsden is a place that holds great meaning for me and whose care and expertise are life-changing for so many people," Catherine wrote on Instagram.