Prince William makes 1st official appearance amid King Charles, Princess Kate health issues

Two of the highest-profile members of Britain's royal family, King Charles III and Princess Kate, are currently facing health issues that are keeping them out of the public eye.

In their absence, the few remaining members of Charles' slimmed-down monarchy are staying active to keep the royal schedule full.

Prince William, the eldest son of Charles and the heir to the throne, stepped in for his father Wednesday at Windsor Castle, leading an investiture ceremony.

The ceremony marked the first public engagement for William since mid-January, when Kate underwent what Kensington Palace described as a "planned abdominal surgery."

Kate's surgery left her hospitalized for nearly two weeks.

The mother of three is now recuperating at the family's home in Windsor, England, but is not expected to resume public duties until the spring.

Princess Anne, Charles' sister, visited a community center in Nottinghamshire on Tuesday, the day after it was announced by Buckingham Palace that Charles, 75, had been diagnosed with cancer.

Anne, the second eldest of Queen Elizabeth II and Prince Philip's four children, did not comment on her brother's diagnosis during the outing, keeping the focus of her engagement on the work at hand, learning about a local mental health initiative.

Anne, 73, is already well-known for her devotion to royal service, a trait she shared with her late mother, Queen Elizabeth II.

On the royal family's website, Anne, who is 16th in line to the throne, is described as having "one of the busiest working schedules of any member of the royal family."

Also maintaining a busy schedule of royal engagements is Queen Camilla, who is doing so while also supporting her husband Charles following his cancer diagnosis.

The palace has not specified what type or stage of cancer Charles has, or what type of treatment he is undergoing or plans to undergo, but officials said he has been "advised by doctors to postpone public-facing duties" for the time being.

Camilla was by Charles' side Tuesday as the two left Buckingham Palace for Sandringham, the king's estate in Norfolk, England.

Last month, while Charles was out of the public eye for several days for treatment for an enlarged prostate, Camilla maintained her public schedule, continuing her engagements on her own.

The day after Charles' Jan. 29 discharge from The London Clinic, Camilla hosted a reception at Windsor Castle for a new Miniature Library collection there.

The last two remaining senior working royals able to help as Charles and Kate are recuperating are Charles' younger brother Prince Edward and his wife Sophie, the Duchess of Edinburgh.

Both Edward and Sophie have continued on with their usual public engagements over the past few weeks.

Neither Kensington Palace nor Buckingham Palace have said when exactly they expect Kate and Charles to return to their respective public duties.