King Charles III has given his daughter-in-law Kate Middleton a new historic title.

On Tuesday, the British monarch appointed the Princess of Wales a Royal Companion of the Order of the Companions of Honour. The mother of three is the first member of the royal family to ever be appointed to the Companions of Honour.

According to Harper’s Bazaar, the order was founded by King George V in 1917. It recognizes accomplishments in art, science, medicine and public service. The outlet noted that it is one of the most distinguished royal appointments.

KATE MIDDLETON, KING CHARLES MET PRIVATELY BEFORE SHE REVEALED CANCER DIAGNOSIS: REPORT

Kate Middleton and King Charles smiling and standing side by side

Kate Middleton is the first member of the royal family to ever be appointed to the Companions of Honour. (Danny Martindale/WireImage/Getty Images)

The order currently has 65 members, including Elton John, Paul McCartney and J.K. Rowling. The new list of honors was revealed by Buckingham Palace on Tuesday, April 23, which is also known as St. George’s Day in the U.K.

Harper’s Bazaar also revealed that at the same ceremony, which took place at St. George’s Chapel at Windsor Castle, Charles appointed his eldest son, Prince William, as Great Master of the Most Honourable Order of the Bath. 

Charles held that same order when he was the Prince of Wales from 1974 to 2022. According to the outlet, his predecessors include Prince Henry, Duke of Gloucester (1942–1974), and Prince Arthur, Duke of Connaught and Strathearn (1901–1942).

King Charles wearing a blue suit and smiling next to two people inside the palace

From left: King Charles was presented with the first banknotes featuring his portrait from the Bank of England's governor, Andrew Bailey, and Sarah John, the bank's chief cashier, at Buckingham Palace in London on April 9. (Yui Mok - WPA Pool/Getty Images)

The king’s wife, Queen Camilla, was appointed as Grand Master and First or Principal Dame Grand Cross of the Most Excellent Order of the British Empire. The appointment was previously held by the king’s father, Prince Philip, from 1953 to 2021.

The Duke of Edinburgh, Britain’s longest-serving consort, died in 2021 at age 99.

Middleton’s latest royal title is being seen as a sign of support from Charles, 75. Both the monarch and the princess are battling cancer.

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Kate Middleton in a white top with navy stripes sits on a bench to announce she has cancer

Kate Middleton announced to the world she had cancer in a pre-recorded message shared in March. (The Prince and Princess of Wales Twitter)

Charles is known to be very fond of Middleton, 42. During his state visit to Kenya in 2023, the monarch recalled how William proposed to Middleton in the country in 2010. He called her "my beloved daughter-in-law" at his address.

Middleton is also known for showing affection toward the king. During public engagements, the pair exchange hugs and kisses on the cheek.

The king "has always had a very good bond with her," author Sally Bedell Smith previously told People magazine

"She's interested in artistic things, and she appreciates art and culture, so [she] has an affinity with the king over that."

King Charles and Kate Middleton sharing a kiss on the cheek

King Charles III and the Princess of Wales are known to have a warm relationship. (Max Mumby/Indigo/Getty Images)

Smith, who penned "George VI and Elizabeth: The Marriage That Saved the Monarchy," said the king and princess now have another shared bond over their cancer diagnosis.

"Obviously, they have this in common and can only bring them closer," she noted. "It is a source of reassurance and consolation for both of them."

Charles was diagnosed with a form of cancer and is undergoing treatment, Buckingham Palace announced in February. A "separate issue of concern" was identified during Charles' "benign prostate enlargement" procedure at the London Clinic.

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Queen Camilla holds on to King Charles as they attend Sunday service after announcing he has cancer

King Charles and Queen Camilla attend church service on Feb. 11. (Max Mumby/Indigo/Getty Images)

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"Subsequent diagnostic tests have identified a form of cancer," the palace said in a statement at the time.

In a video shared in March, the Princess of Wales revealed that she, too, is battling a form of cancer, and has been undergoing preventative chemotherapy treatment.

Fox News Digital's Tracy Wright and The Associated Press contributed to this report.