The Princess of York captioned the photograph saying: “August and his cousin Sienna love going to the London Zoo.
“It’s part of the Zoological Society of London @zsllondonzoo a global wildlife conservation charity that helps to restore habitats and protect wildlife. Every time you visit you are supporting their work.”
The photograph showed Sienna and Eugenie’s son August side by side looking at the penguins in the London Zoo.
Although Sienna’s face cannot be seen, it is the first official picture shared by a member of the Royal Family of the one-year-old.
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Princess Beatrice does not have an official Instagram account, but her husband Edoardo similarly has not shared any official photographs of their daughter.
In the picture, Sienna looked beautiful in a “Baby Retro Pile Fleece Jacket with Live Simply Whale Patch” from the brand Consortium.
The jacket costs £69.99 and looked effortlessly cool on the one-year-old royal.
Its description says: “Soft, cosy 100 percent recycled fleece jacket keeps babies warm.
“It has a slightly pointed hood (a nod to our gnome friends), snapped placket, patch pockets, rib-knit cuffs and a shirttail hem for extra coverage.”
Sienna paired the fleece jacket with some light blue denim jeans, which featured two back pockets and classic ankle cuff detailing at the bottom.
In addition, Sienna wore some black boots with white fluffy detailing at the top to provide some warmth and white soles.
Princess Beatrice’s daughter appeared to have strawberry blonde hair which looked incredibly similar to her mother’s hair colour when she was a toddler.
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In the same picture, August Brooksbank, two, who is the son of Princess Eugenie and Jack Brooksbank, wore a beige jacket with a white fluffy colour and hemline.
He paired this jacket with dark blue denim jeans and very dark brown boots to complete his dapper outfit.
Unlike his younger cousin, August has been shared on social media many times and even made official appearances at the Platinum Jubilee in 2022.
Princess Eugenie is currently pregnant and is expecting her second child this upcoming summer.