Princess Kate and Prince William to follow new rule for Princess Charlotte's birthday photo

The Prince and Princess of Wales made a major change when sharing a new portrait of Prince Louis to mark his birthday last month – and they're expected to do the same for their daughter, Princess Charlotte.

The Princess will celebrate her ninth birthday on Thursday 2 May and it's likely that Prince William and Kate will post the image of Charlotte on social media to mark the occasion.

It comes after the couple released an unedited new photo of Louis straight to social media, rather than under embargo to the press as was the tradition, to mark his sixth birthday on 23 April.

The snap of the Prince was posted on his actual birthday rather than the night before, as had always been the case.

It was understood to be due to the unprecedented time the family is experiencing as Kate continues her cancer treatment, with the couple wanting to thank the public for their well-wishes.

ROYAL CHILDREN LATEST

• Prince William gives heartwarming update on Princess Kate and their three children

• Sensible Princess Charlotte 'likes to fit in and do the right thing'

• King Charles' special nod to George, Charlotte and Louis on first royal outing didn't go unnoticed

• Prince Louis' birthday photos all have this in common – did you notice?

• Princess Charlotte was gifted a crown during secret Strictly visit - and Prince Louis had the best reaction

It also comes after a sweet family shot of the Princess with George, Charlotte and Louis released on Mother's Day sparked speculation - it was withdrawn by picture agencies over concerns it had been manipulated after discrepancies were spotted in the photograph.

Kate issued a public apology stating: "Like many amateur photographers, I do occasionally experiment with editing. I wanted to express my apologies for any confusion the family photograph we shared yesterday caused. I hope everyone celebrating had a very happy Mother's Day. C."

Less than two weeks later, the Princess issued an emotional video message to the nation, announcing she was undergoing chemotherapy after post-op tests from her abdominal surgery found cancer had been present.

In 2015, Kate became the first member of the royal family to take the first official photographs of a royal baby, with the then Duchess of Cambridge releasing her own images of newborn Charlotte being held by her big brother George at the family home, Anmer Hall, in Norfolk.

Since then the Princess has taken all of the official photographs of her children to mark occasions such as birthdays, Father's Day and their first day at school.

Charlotte's eighth birthday last year came just a few days before the King's coronation at Westminster Abbey.

Kate snapped her beaming daughter in a white floral dress near the family's home in Windsor. Further images released later in the day also showed the Princess with the family's black cocker spaniel, Orla.

Princess Charlotte's last public appearance

The Prince and Princess of Wales's daughter was last seen publicly as she joined her parents and brothers on the walk to church for the annual Christmas Day service.

Charlotte, dressed in an olive green coat, chatted with her second cousin, Mia Tindall, as the youngsters chatted to members of the public who had gathered to greet the royals.

Prior to Christmas Day, the three Wales children attended their mother Kate's festive concert at Westminster Abbey, where they posted handwritten cards for vulnerable children.

Just a few days after their outing, Kensington Palace shared footage of George, Charlotte and Louis volunteering with mum Kate at a local baby bank in Maidenhead. Take a look in the clip below...

Co-CEO of The Baby Bank, Lauren Hall, exclusively told HELLO! at the time: "They were really excited to help out, which was lovely… Charlotte seems to quite like organising things and was very keen to do some bags for people of her own age as well as some younger, more baby ones. She was quite keen to do a little clothing pack for a baby."