Princess Eugenie shared a sweet message for her sister Beatrice to mark her 37th birthday on Friday.
Eugenie, who is two years younger than Beatrice, shared five images of her sister, whose birthday is on August 8, on her post on Instagram.
The images were accompanied by a caption in which she referred to her as 'dearest Beabea'.
'Happy happy birthday to my dearest Beabea.. my big sissy, the best in the entire world,' it said.
The first picture in the post showed Beatrice smiling, while the other images all showed the two sisters together, with one also featuring their mother, Sarah Ferguson too.
One of the images showed Eugenie and Beatrice holding up panini and smiling, while another showed the two sisters wearing floral frocks and grinning as they posed for the shot.
Many people took to the comments section to share their own well wishes with the royal.
One wrote: 'Beautiful ladies with a beautiful mama. Happiest of birthdays.'
Another added: 'Beautiful and lucky! 8/8/1988. I walked past the hospital on my way to work that morning and I was SO HAPPY!'
'It's lovely to see these ladies shine and blossom into strong confident women!' said a third.
A further Instagram user simply said: 'Happy Birthday Princess Beatrice.'
'Absolutely stunning photos. Thank you for sharing. HB,' another wrote.
Among the many commenters on the post was Beatrice's husband Edoardo Mapelli Mozzi.
He simply posted five hearts in response to Eugenie's touching comment.
Edo also shared his own Instagram post wishing his wife a happy birthday.
It featured an image of Beatrice wearing a fascinator and cream frock, alongside a gushing caption.
Beatrice's birthday comes just weeks after her wedding anniversary - she tied the knot with Edoardo on July 17, 2020.
The couple celebrated their fifth wedding anniversary this year.
Edo, with whom Beatrice shares two children, marked their fifth anniversary with a sweet post on Instagram.
He shared a snap of the couple posing together on a beach in Scotland, which he accompanied with the sweet caption.
It said: 'Happy 5th Anniversary to my incredible partner, the most beautiful and amazing wife. I cherish every moment we've spent together and am deeply grateful for our journey. Here's to countless more years filled with laughter and tons of love!'
Since tying the knot five years ago, Edo and Beatrice, 36, have gone on to welcome two daughters.
Their eldest daughter, Sienna Elizabeth Mapelli Mozzi, three, was born in September 2021.
She was followed by Athena Elizabeth Mapelli Mozzi, who was born in January this year.
It has been reported that Beatrice refers to Wolfie, nine— the son Edo shares with former partner Dara Huang— as her 'bonus child'.
Edo and Beatrice tied the knot at Royal Chapel of All Saints, in the grounds of Prince Andrew and Sarah Ferguson's home of Royal Lodge, in Windsor Great Park, surrounded by close family including the late Queen Elizabeth II and the Duke of Edinburgh.
Princess Eugenie and her husband Jack Brooksbank attended, as did Edo's son Christopher, known as Wolfie.
They had been due to wed on May 29 at the Chapel Royal in St James's Palace, but those plans were scrapped due to the pandemic.
Instead, they exchanged vows on this day five years ago at the Royal Chapel of All Saints, in the grounds of Royal Lodge, Beatrice's childhood family home in Windsor Great Park.
The intimate ceremony, which adhered to social distancing measures, was attended by around 20 guests.
It was strikingly low-key compared to Princess Eugenie's extravagant 2018 nuptials, which featured a carriage procession around Windsor and incurred around £2 million in public expenses.