Kate Middleton and Prince William are thankful for the warm wishes their sons received from supportive royal fans.

The Duke and Duchess of Cambridge have a number of celebrations for their kids in the past months. In June, their youngest child, Prince Louis, was baptized. In July, their eldest son, Prince George, turned 5. So, the family released thank you cards to those who spent some time to write a note for the royal children.

One user shared a snap of the thank you card she received. It featured a giggling photo of Prince Louis taken on his christening by Matt Porteous.

"Fantastic postcard from the Cambridges thanking me for sending my good wishes to HRH Prince Louis of Cambridge on the occasion of his christining. #royalletter #royalreply #Royal #princelouisofcambridge #princelouis," loopycrown3 wrote on Instagram.

Many were very pleased with the said photo, but according to Alice Scarsi, it was not meant to be released to the public. The said photo was one of the pictures taken during the family's private moments. However, Prince William and Middleton found it too adorable not to share to the public.

"The Duke and Duchess of Cambridge have released an additional photograph taken following the christening of Prince Louis," the palace wrote on Twitter. "The Duke and Duchess hope that everyone enjoys this lovely photograph of Prince Louis as much as they do."

Middleton also released another thank you card for Prince George. It features the third heir leaning against a wall in Prince Charles' gardens at Clarence House with a broad smile on his face.

Prince George wore a white short-sleeved shirt with blue buttons. He paired it with his trademark shorts. The photo was also taken by Porteous after Prince Louis' christening.

"Wonderful postcard from the Cambridges thanking me for sending my birthday wishes to HRH Prince George of Cambridge. #royalletter #royalreply #Royal #princegeorgeofcambridge #princegeorge," loopycrown3 wrote on Instagram.

In related news, Prince William just revealed his children’s favorite bedtime story. According to Duke of Cambridge Prince George, Princess Charlotte and Prince Louis love "Gruffalo." The royal dad of three has met Julia Donaldson and Axel Scheffler, the author and illustrator of the book on Monday evening for the conservation event he hosted.