Prince William's children -- Prince George, Princess Charlotte and Prince Louis -- made special cards for their late grandmother, Princess Diana, as the United Kingdom celebrated Mothers' Day on March 14.

The Cambridges shared the children's artwork and messages for "Granny Diana" in an Instagram post. On Charlotte's card, the almost 6-year-old child wrote that her father is missing his mother.

William was only 15 years old when Diana died in a car accident in France in 1997. The children never got to meet their iconic grandma but their father and mother keep her memories alive.

In July 2021, William will dedictate the unveiling of Diana's statue at Kensington Palace. Sources, however, said that it might be impossible to see the Duke of Cambridge reunite with his brother, Prince Harry, in front of the cameras for this special event because of their growing rift.

In a separate post, George, Charlotte and Louis also baked a cake to celebrate Mother's Day. The Cambridges also shared a throwback photo of Kate's mom, Carole Middleton, with a young Kate. Carole was pregnant with Kate's youngest sibling, James, in the photo while someone at the back was carrying baby Pippa, Kate's sister.

Meanwhile, Queen Elizabeth also had a tribute for the Queen Mother. The Royal Family Instagram account shared a throwback picture of the Queen as a budding teenager with her mother next to her.

Queen Elizabeth also received a tribute from her son and heir, Prince Charles. The Prince of Wales shared an old photo of him and his mother laughing together during a royal event. The other photo is of Camilla, the Duchess of Cornwall, and her mother, Rosalind, who passed away in 1994.

According to Town & Country magazine, Harry arranged to have flowers laid out on his mother's grave on the family estate owned by the Spencers in Althorp. Diana's grave is in the middle of a lake in the Princess of Wales' childhood home.

Princess Eugenie, William and Harry's cousin who is the only member of the royal family with a personal social media account, shared a new photo of her son, August, who was born in February. She posted a second photo with her mother, Sarah Ferguson, the Duchess of York.

Meanwhile, George, Charlotte and Louis have returned to Kensington Palace after staying in the country for months due to the lockdown. The two older Cambridge kids are back to in-person classes in London.