William, 42, and Kate, 43, shared the portrait on their joint Instagram account, writing in the caption, "Happy 10th Birthday ... photographer—snapped a black-and-white photo of George in ...

“Happy 10th Birthday Princess Charlotte ... completing her look with a blue backpack and black pants. Middleton took the sweet snap with an iPhone, a royal first, during a hike in Cumbria.

"Happy 10th Birthday Princess Charlotte!," the photo's caption reads. The only daughter of William and Kate, Charlotte's full name, Charlotte Elizabeth Diana, is a tribute to her great-grandmother ...