Prince William, Prince George, Princess Charlotte and Kate Middleton
Prince William and Kate Middleton reportedly arranged a “Free Solo” private screening for their son Prince George. Pictured: Prince William, Prince George, Princess Charlotte and Middleton arrive at the Victoria Airport on Sept. 24, 2016 in Canada. Getty Image/Chris Jackson

Kate Middleton and Prince William thanked those who greeted Princess Charlotte on her fourth birthday.

The Duke and Duchess of Cambridge were very thankful to those who gave them warm wishes for their only daughter’s birthday. Princess Charlotte turned 4 years old on May 2.

Gert’s Royal Replies received one of the sweet Thank You cards from Prince William and Middleton following Princess Charlotte’s special day. On the side, the card features an official birthday portrait of Princess Charlotte, which the Duchess of Cambridge captured herself.

“The Duke and Duchess of Cambridge appreciated your kind thought in writing to Princess Charlotte as you did on the occasion of her fourth birthday,” the card read as shown on Twitter.

“This was greatly appreciated by Their Royal Highnesses who send you their best wishes.”

Aside from greeting Princess Charlotte on her birthday, Gert’s Royal Replies had gone the extra mile by congratulating Middleton after she was appointed as Dame Grand Cross of the Royal Victorian Order. And the card they received also addressed their warm wishes for the Duchess of Cambridge.

“Their Royal Highnesses are grateful to you for taking the trouble to write as you did and were touched by your kind words of support regarding Her Royal Highness's recent appointment as Dame Grand Cross of the Royal Victorian Order (GCVO),” the letter read.

“It really was most thoughtful of you... The Duke and Duchess of Cambridge have asked me to send you their warmest thanks and best wishes.”

Prince William and Middleton were last seen together last Saturday at Archie’s baptism. However, the Duke and Duchess of Cambridge attended the event without their three kids, Prince George, Princess Charlotte and Prince Louis.

According to body language expert Traci Brown, Prince William and Middleton were showing signs of stress as they looked “stiff” even for royals. Meanwhile, many netizens pointed out the Duke of Cambridge’s “sour” and “unhappy” expression and slammed him for looking as if he didn’t want to be there.