Dave Benett/Getty; Princess Eugenie/Instagram
"Happy 2nd Birthday to our boy Augie.. you are our worlds greatest joy," Princess Eugenie, 32, wrote. "Keep dancing and smiling my angel. Xx"
The Anti-Slavery Collective co-founder shared adorable footage of her son running down a path at a park, laughing, smiling and dancing. Posting more home videos of August on her Instagram Story, the carousel began with a bundled-up August running through a large puddle with dad Jack, 36, close behind.
In the second clip, August babbled at a gate to say bye to his father.
"Say, 'I love you Dada!' " Eugenie coached him from behind the camera.
The tribute closed with two photos from an outdoor excursion, where Jack walked hand-in-hand with August, followed by Eugenie in the same spot with their son.
"Happy Birthday Augie," she wrote over the photo, using the family nickname previously revealed by her mother, Sarah Ferguson.
August's birthday comes two weeks after Buckingham Palace announced the happy news that Princess Eugenie is pregnant with her second child.
"Princess Eugenie and Mr. Jack Brooksbank are pleased to announce they are expecting their second child this summer," courtiers said in a statement on Jan. 24. "The family are delighted and August is very much looking forward to being a big brother."
Princess Eugenie also made a post on her Instagram page, sharing a photo of August kissing her belly and wrapping his arms around her legs.
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"We're so excited to share that there will be a new addition to our family this summer," the niece of King Charles III wrote of the photo, which was taken by her husband.
Princess Eugenie and Jack's second child will be the first of Queen Elizabeth's great-grandchildren born following her death in September. The new baby will be 13th in the line of succession to the British throne, just after August.