Prince William and Kate Middleton celebrate their 13th anniversary with never-before-seen wedding photo

Prince William and Kate Middleton are celebrating their 13th wedding anniversary, with the couple even sharing a never-before-seen photo.

Fans took to social media to send their well-wishes tot he couple, who tied the knot at Westminster Abbey back in 2011. It's said that as many as 37 million people watched the event in the UK alone.

Since the the Prince and Princess of Wales have welcomed three children to the world - Prince George, Princess Charlotte and Prince Louis.

The couple marked the occasion with a photo that was previously never released to the public, with fans clearly delighted to see the new image.

"Oh Wow! This is so beautiful thank you for sharing a new picture," wrote one fan, with another adding: "Happy Anniversary you gorgeous couple. Sending love and hugs in abundance to you both. Here's to many more years of happiness for you two love birds."

Another wrote: "Thank you so much for sharing this photograph with us, Your Royal Highnesses! We all remember your special day with so much love."

Tough year for the royal family

While celebrating the wedding anniversary will certainly bring joy to the royal family, it has been a tough year for them.

The Princess of Wales is currently receiving treatment for cancer after undergoing abdominal surgery at the start of the year.

Nevertheless, William hasn't wavered in his support for the Princess of Wales, who shared her diagnosis with the world just a few weeks ago.

The Prince of Wales is also dealing with the King Charles' battle with cancer. The 75-year-old is still undergoing treatment, but his medical team are said to be "pleased with eh progress made so far."

That's why Charles has been allowed to return to public duties, as he'll attend a cancer treatment clinic with Queen Camilla on Tuesday. Buckingham Palace made the announcement last Friday, with the occasion even more poignant given Charles and Kate's battles.