Kate Middleton will be joining Prince William, King Charles, Queen Camilla, and other royals at a black-tie dinner-dance celebration for Sophie, Duchess of Edinburgh's 60th birthday, a source tells 'The Sun.

Sophie, the Duchess of Edinburgh is marking a milestone birthday! She turned 60 on Jan. 20, and friends and former colleagues have been honoring her contribution to the royal family – amid the release of the duchess' stunning new portrait.

Photographer Christina Ebenezer also shared her favorite part of the photo shoot Sophie, the Duchess of Edinburgh is starring in a new portrait for her 60th birthday, and the photographer behind the camera is sharing an unseen snap from the photo session.

Sophie, the Duchess of Edinburgh is turning 60 in style. The royal—who marked her milestone birthday on Monday, January 20—released a trio of stunning portraits to commemorate the special occasion over the weekend that seemingly included a subtle sartorial nod to her grand new title.

A new photograph of the Duchess of Edinburgh looking happy and relaxed has been released to celebrate her 60th birthday. The duchess is set to celebrate the milestone at home with the Duke of Edinburgh on Monday at her Bagshot Park home.

I love how she is not afraid to try new things and she makes beautiful choices,” designer Suzannah Crabb of royal favorite Suzannah London tells PEOPLE