Prince Louis' Sweet Secret Message to Kate Middleton's Parents Revealed at Carol Concert

Prince Louis is giving thanks this Christmas season.

The youngest son of Kate Middleton and Prince William wrote a sweet message to his grandparents at the fourth annual Together at Christmas carol service on Friday, Dec. 6.

The 6-year-old, who attended the festive event alongside siblings Prince George, 11, and Princess Charlotte, 9, placed a note on the "Kindness Tree" set up outside of Westminster Abbey in London, where the holiday event took place.

"Thank you to Granny and Grandpa because they have played games with me," he wrote on the note, referring to his maternal grandparents, Carole and Michael Middleton.

On Sept. 9, the Princess of Wales, 42, announced in an intimate video that she had completed chemotherapy after previously revealing that she was undergoing treatment for cancer in March. In the video, which was shared on the official Kensington Royal social media accounts, Kate's parents can be seen playing games at a table with Louis, Prince George, 11, Princess Charlotte, 9, as well as Prince William, 42, and Kate.

Related: Kate Middleton Makes Rare Comment About Her Cancer Journey: 'I Didn't Know' What This Year 'Was Going to Be'

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"Her parents are an enduring factor in the upbringing of their grandchildren," a palace insider told PEOPLE back in March. The Middletons reportedly have sleepovers with the trio of siblings and accompany Kate on school drop-offs occasionally.

Carole, 69, and Michael, 75, attended Friday's carol service hosted by their daughter, as did their other children, James Middleton and Pippa Middleton. While all the Middletons were present to support the Princess of Wales, King Charles and Queen Camilla were absent.

Another sweet Louis moment was revealed when Kate Mansey, a reporter from The Times, overheard Princess Kate speaking to singer-songwriter and actress Paloma Faith. While discussing the ballet performance, which was a surprise revealed during the service, Kate revealed that Louis adorably struggled to keep the surprise a secret from his sister Charlotte, who takes ballet lessons.

"This morning, he said, 'Mummy, please can I tell her - I’m bursting.' " the royal holiday host revealed.

Related: Kate Middleton and Princess Charlotte Share Sweet Fashion Moment with Matching Velvet Bows at Carol Service

Charlotte was even seen standing like a ballerina with her feet in third position at one point during the service.

The palace said that 1,600 people would convene in Westminster Abbey on Dec. 6 for the holiday concert, welcoming those who have supported others in their communities through personal relationships, work or volunteering, plus others who experienced difficult times this year.

Read the original article on People