Princess Kate popped up in the background of an adorable Middleton family photo

When James Middleton got married in 2021, his older sister Kate, the then-Duchess of Cambridge, was obviously in attendance.

However, no photos showing her at the event were released — until now.

For Mother's Day, James shared an adorable photo of himself hugging his mum Carole Middleton on his wedding day. In the photo, both are smiling brightly. He captioned it: "You make my world go around ... Happy Mother’s Day to all the mothers out there and especially to this one"

Commenters were quick to point out that Kate is visible — though blurry — in the background of the picture. She's styled her long brown hair down, and looks to be wearing a puff sleeve dress in a pale colour.

"Kate and Pippa in the back," wrote one royal fan, adding a red heart emoji.

"Do I spy Kate and Pippa in the background?!" asked someone else.

In case you're getting confused, Kate, Pippa and James are the three children of Carole and Michael Middleton.

James isn't the only one to have made a big deal out of Mothering Sunday, however. The Prince and Princess of Wales also shared an exclusive family photo of Kate sitting in a tree with the three Wales children, Prince George, Princess Charlotte, and Prince Louis.

"Happy Mother’s Day from our family to yours," they wrote, adding a red heart emoji and crediting photographer Matt Porteous.

Meanwhile, King Charles and Queen Consort Camilla also dedicated a post to their late mothers, with a photo of the King as a toddler with Queen Elizabeth, and one of Camilla as an adult with her mother Rosalind Shand.

They captioned their poignant post: "To all mothers everywhere, and to those who may be missing their mums today, we are thinking of you and wishing you a special #MothersDay."

As you know, the King acceded to the throne just months ago, following the death of his mother the Queen at age 96.