Prince William misses royal event citing 'personal matter'

Prince William was forced to miss a royal engagement Tuesday due to a "personal matter," Kensington Palace said.

The personal matter was not related to his father King Charles III's health, ABC News has confirmed.

William was scheduled to attend a service of Thanksgiving for King Constantine of Greece at St. George's Chapel in Windsor Castle, but was forced to drop out of the ceremony Tuesday.

"Unfortunately, The Prince of Wales is no longer able to attend the King Constantine Memorial Service this morning due to a personal matter," the palace said in a statement, declining to share further details.

William's absence comes as both the king and William's wife Kate, the Princess of Wales, face separate health issues.

William was expected to attend Tuesday's service without Kate, who continues to recover at home from abdominal surgery. The 42-year-old mother of three spent nearly two weeks in the hospital after undergoing the surgery in mid-January.

Kate, whose last public appearance was on Christmas Day, is not expected to resume her public royal duties until later this spring.

In the absence of Kate and Charles, who was diagnosed with an undisclosed type of cancer earlier in February, it has been left to William, as well as Charles' wife Queen Camilla, to lead the royal family as the two most senior royals currently undertaking public engagements.

Camilla formally led the British royal family at Tuesday's service of Thanksgiving, which was attended by members of King Constantine's family as well as other royals from around the world. Other members of Britain's royal family who attended the service included Prince Andrew and Sarah Ferguson and their daughter and son-in-law, Princess Beatrice and Edoardo Mapelli Mozzi. Charles' sister Princess Anne, along with her daughter Zara Tindall and son-in-law Mike Tindall, also attended the service.

William is said to have personally called the late king's family ahead of the service to let them know he would not be able to attend.

William's absence from the service marked a very rare occurrence, as royal family members rarely miss an engagement for a personal reason.

William took time off from public engagements while Kate was hospitalized following her surgery but resumed his duties in early February. On his first day back, Feb. 7, William stepped in for his father to lead an investiture ceremony at Windsor Castle.

Since announcing Charles' cancer diagnosis earlier this month, Buckingham Palace has not specified what type or stage of cancer Charles has, or what type of treatment he is undergoing.

Officials said only that Charles, 75, has started "a schedule of regular treatments," and has been "advised by doctors to postpone public-facing duties" for now.

Charles has still been seen publicly since his diagnosis, including attending church with Camilla in Sandringham. Last week, the palace released new photos of Charles reading some of the more than 7,000 cards and letters the palace says the king has received since his diagnosis was shared with the public.