Princess Eugenie shared an adorable photograph of her son August alongside his cousin during a family trip to the zoo.

In the image, August is joined by his young cousin Sienna, who is the daughter of Princess Beatrice. The pair are side by side with their hands pressed against the glass of an enclosure, as they watch penguins swimming past underwater.

Then, in the following two photographs, August stands in the centre of an exhibition featuring footage from the BBC's Natural History Unit, including amazing deep sea scenes and images of the planet surrounded by shooting stars.

What to read next

The final photograph shows Princess Eugenie's husband walking beneath a flower-covered tree alongside August, as they follow a dog which appears to be a corgi. Explaining why she chose this photo in particular, Eugenie wrote, "because I love them and they love nature."

Princess Eugenie shared the post to mark Earth Day on Saturday (22 April) in order to highlight and celebrate, "our planet and [the] people doing amazing things that help protect it", she wrote in a caption.

Also included in the post are photographs of the Princess getting to grips with some oysters with the Blue Marine Foundation's initiative, which she said, "is restoring coastal marine life with a collection of partners making it one of the most ambitious environmental projects in the UK!" She added that "one oyster can clean up to 200L of water a day."

This Monday marked a special birthday for one of the other royal children, as Prince Louis turned 5. To celebrate, the Prince and Princess of Wales shared some adorable new snaps of their youngest son playing in a wheelbarrow, pushed along by his mother, Kate.