Breaking News Update: The British Royal Family is once again plunged into mourning following the loss of another grandchild. Reports identify him as…

From the Aberfan mining disaster in season three to the assassination of Lord Mountbatten in season four, “The Crown” has never shied away from showing some of the darker chapters in the history of the modern British royal family.

However, the latest season of the Netflix series has served up one of the most heartbreaking stories so far, with the tragic death of Leonora Knatchbull, the youngest daughter of the Windsors’ close family friends Norton and Penelope Knatchbull.

The young girl — who was the great-granddaughter of Louis Mountbatten, making her a distant cousin of King Charles III — was five years old when she passed away from kidney cancer on October 22, 1991.

However, Leonora and her family were not just connected to the British royal family. Per an obituary from The Herald in Scotland, she was the goddaughter of King Juan Carlos of Spain.

According to the outlet, it was during a holiday in Majorca in August 1990 with her parents and her older siblings, Nicholas and Alexandra, that she started showing signs of illness.

Acting quickly, the former king “arranged for her to be flown home” early in order to be checked out by medical professionals. It was soon confirmed that she was suffering from a tumor in her kidney.

In “The Crown,” Princess Diana (Elizabeth Debicki) mentions that she is Leonora’s godmother, but this appears to have been made up for the purposes of the show.

In reality, Diana was godmother to one of the Knatchbull children — but it was their eldest daughter Alexandra, not Leonora.

Nevertheless, the late royal, who died six years after Leonora in 1997, was very close to the young girl. She was one of the last people to visit Leonora at St Bartholomew’s Hospital “when it became clear her life was ebbing away,” per the Herald.

Diana, along with Charles and sons Prince Harry and Prince William, joined the Knatchbulls during the 1990 trip to Majorca and, as “The Crown” depicts, the families went on another vacation to Italy together in 1991 just a few months before Leonora’s death.

Their friendship is even captured in a sweet photo just a few months before Leonora’s death when the Knatchbulls joined the royals on the balcony of Buckingham Palace to celebrate the annual Trooping the Colour ceremony.

Diana can be seen crouching down next to Leonora and pointing to the sky during the fly-past of the Royal Air Force. The youngster is wearing a bright red outfit paired with a matching hat, which may have been an intentional choice to hide her hair loss following her chemotherapy and radiotherapy treatments.

After her death, Leonora was buried on the grounds of the family estate, and the family set up Leonora Children’s Cancer Fund in her honor in 1994, which was dedicated to “the relief of sick, distressed, or needy children in any part of the world.”

The charity was later merged with another set up for Leonora’s paternal great-grandmother to make The Edwina Mountbatten and Leonora Children’s Foundation. Both Penelope and Alexandra remain trustees of the charity today.