Princess Eugenie congratulates Princess Beatrice and Edo on pregnancy news with unseen photos

Princess Eugenie has publicly shared her congratulations on her sister's royal baby.

Posting two new photos of Princess Beatrice and Edoardo Mapelli Mozzi on Instagram on Thursday (Friday morning AEST), the new mum shared her excitement at the new addition to the family — a cousin for her young son August Brooksbank.

Eugenie, 31, also revealed her pet name for her big sis is "Beabea".

"It's World Bee Day!! A day to celebrate nature's most badass little friend with their black and yellow stripes," the caption began.

⁣"But our furry little friends have to share today with my big sis Bea who's got a little one on the way. ⁣

RELATED: Princess Beatrice's royal baby: What we know so far about Baby Mapelli Mozzi

⁣"Beabea and Edo huge congratulations on your news — can't wait to meet the little one⁣."

The previously unseen photos include one from the couple's surprise wedding last July, which appears to have been taken by Eugenie herself.

Princess Eugenie took the couple's engagement photos, which were released when they announced that news in September 2019.

Beatrice and Edo's big royal wedding, originally planned for May 29, 2020, had to be cancelled due to the coronavirus pandemic.

They then tied the knot in a secret and intimate ceremony attended by just 20 people, including Beatrice's grandparents the Queen and Prince Philip, as well as parents Prince Andrew and Sarah Ferguson.

The couple only released four official photos from their big day on July 17.

Princess Beatrice's pregnancy was announced by Buckingham Palace yesterday, in a simple two-line statement.

"The Queen has been informed and both families are delighted with the news," Buckingham Palace said in a statement.

The 32-year-old is due to give birth sometime in the UK autumn, meaning any time between September and November this year.