Kate Middleton and Prince William send sweet reply to girl who invited Prince George to her birthday

While the Duke and Duchess of Cambridge receive a plethora of invitations to various events around the world, it was their son Prince George who was the subject of a rather sweet invite recently.

The heir to the British throne caught the eye of a six-year-old girl who generously sent him an invitation to her birthday, but unfortunately, he was unable to attend.

However, his parents made sure the invite was replied to.

A letter sent from Kensington Palace on behalf of the couple was shared on Twitter, under the username @xxAimeeRoxyxx.

"The Duke and Duchess of Cambridge have asked me to thank you for your letter, in which you invite Prince George to your 6th Birthday party," the letter read.

"I am sorry that it took so long to reply. Their Royal Highnesses were extremely grateful for your kind invitation. Having given careful consideration to the possibilities, however, I very much regret that Their Royal Highnesses reluctantly feel they have to decline.

"Nevertheless, I hope that you enjoyed your birthday. The Duke and Duchess of Cambridge were immensely touched that you should take the trouble to write as you did to their son, Prince George.

"It really was most thoughtful of you and Their Royal Highnesses have asked me to send you their warmest thanks and best wishes."

How cool?