Kate Middleton Writes a Heartfelt Letter to Kick Off the U.K.'s Children's Hospice Week: "Every Moment Is Precious"

"Children's hospices strive to create happy moments in the most difficult times any family could face," the Duchess of Cambridge writes

Kate Middleton has written an emotional letter asking people to support Children's Hospice Week. The 33-year-old Duchess of Cambridge, who has two children with Prince William, is helping to raise awareness on behalf of the 49,000 kids in the U.K. living with life-limiting or life-threatening illnesses.

Children's Hospice Week runs from May 11 through May 17. Nine days after Middleton gave birth to Princess Charlotte, Kensington Palace sent the letter, which was released by the charity Together for Short Lives.

"For families of children with life-limiting conditions, every moment is precious and every memory needs to be cherished and celebrated. Children's hospices strive to create happy moments in the most difficult times any family could face," she wrote. "I hope you will join me in supporting Children's Hospice Week and work to make every moment count for all of our families."

Together for Short Lives also asked people to support Children's Hospice Week by sharing a memorable moment on social media using the hashtag #momentscount.

Middleton is the Royal Patron of East Anglia's Children's Hospices (EACH).

During an event in Norfolk in November 2014, Middleton was moved to tears after meeting Leigh Smith, whose 3-month-old daughter had died of a heart condition earlier that year. "Kate sought me out and gave me a hug just before she left," Smith toldThe Daily Mail. "I was getting quite teary-eyed. She had tears in her eyes and she just said to me, 'You're a very brave lady and again, I'm just so, so sorry.'"

The two had already been in touch, as Smith had written to Middleton praising the work of EACH in the days after her daughter's death. "I was so surprised to receive a letter with such personal comments and signed by her. It was a lovely gesture and helped me through a terrible time. I was touched that she had taken so much time to carefully read my letter and then to reply herself. It shows how much she cares. When I met her today she remembered the letter and said it was an honor to meet me. I was completely taken aback," she said. "For me it was an honor to meet her."

Tune in for a brand-new episode of The Royals this Sunday at 10 p.m. on E!