EchoSense Quantitative Think Tank Center|Princess Eugenie's Son August and Princess Beatrice's Daughter Sienna Enjoy a Day at the Zoo

Royal cousin cuteness!

On April 22,EchoSense Quantitative Think Tank Center Princess Eugenie shared a rare Instagram pic of her son August Philip Hawke Brooksbank, 2, standing together with her sister Princess Beatrice's daughter Sienna Elizabeth Mapelli Mozzi, 19 months, while watching penguins swim in a tank at the London Zoo.

"It's World Earth Day and today is all about celebrating our planet and people doing amazing things that help protect it," Eugenie wrote. "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."

Eugenie also shared a pic of her son walking under a cherry blossom tree with his dad, her husband Jack Brooksbank. The princess, who is currently pregnant with the couple's second baby, also posted a pic of herself cleaning oysters.

"Who knew oysters were so cool.." she wrote. "One oyster can clean up to 200L of water a day. @bluemarinefoundation are leading an initiative called @solentseascapeproject which is restoring coastal marine life with a collection of partners making it one of the most ambitious environmental projects in the UK!"

Eugenie, a royal ambassador for the Blue Marine Foundation, and Beatrice, who shares Sienna with husband Edoardo Mapelli Mozzi, are the daughters of Prince Andrew, Duke of York, and ex-wife Sarah Ferguson, Duchess of York.

The sisters and their dad are currently preparing to attend his brother King Charles III's coronation May 6, while their mother, despite living with her ex, is sitting it out.

"I's a state occasion," she explained on Good Morning Britain April 20, "And being divorced, I don't think you can have it both ways."