London UK - Catherine, Princess of Wales, on Thursday shared the second photograph of her children in as many weeks, as she stays out of the public eye while battling cancer.

The 42-year-old future queen was credited with taking the photograph of Princess Charlotte to mark her ninth birthday, which was shared on royal social media platforms.

On April 23, she was also said to have been behind the camera for a snap of her younger son Prince Louis on his sixth birthday.

Charlotte is currently third in line to the throne behind her elder brother Prince George (10) and their father, Prince William.

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Both photographs follow a furor in March over a Mother's Day snap of Catherine and her three children that she later admitted to having digitally altered.

The image, said to have been taken by William, was designed to put to bed speculation about her health and whereabouts after she underwent abdominal surgery in January.

But the edits, which saw leading news agencies pull the image, only fuelled rumors and she later admitted in a video that she was being treated for cancer.

The British royal family has been hit by the enforced withdrawal from public life of Kate, as she is widely known, and her father-in-law King Charles III due to cancer treatment.

Neither the king's Buckingham Palace office nor William and Kate's at Kensington Palace have disclosed what type of cancer each royal has.

Charles (75) on Tuesday made his first official public engagement, visiting a cancer treatment and support center in central London.

His return was prompted by doctors who said they were "very encouraged" by the progress of his treatment.