The little girl was born on September 18 and is 11th in line to the throne. While Sienna was added to the list rather quickly, Prince Harry and Meghan Markle's daughter, Lilibet, who was born in June, had to wait almost seven weeks before she was thrown up on the website.
The pair waited a little while to announce the tot's moniker.
"Sienna Elizabeth Mapelli Mozzi 👶🏼Our life together has just begun, and I can’t wait to see all the amazing things that await us," the handsome hunk wrote via Instagram on October 1. "Feeling so much love and gratitude for my amazing wife, baby Sienna and Wolfie. These are the days I never want to forget. This week, a friend said to me the sweetest saying….that with every child you grow a whole new heart 💖A massive thank you to the Midwife and the amazing team at the Chelsea and Westminster Hospital. 🙏🏻 x."
The Royal Family's official Instagram page also posted the same photo Mozzi did.
"Her Royal Highness Princess Beatrice and Mr Edoardo Mapelli Mozzi have named their daughter Sienna Elizabeth Mapelli Mozzi.👣 The couple have said, 'We are all doing well and Wolfie is the best big brother to Sienna,'" the caption read.
Two days after the duo welcomed Sienna, the palace made the big announcement.
"Her Royal Highness Princess Beatrice and Mr Edoardo Mapelli Mozzi are delighted to announce the safe arrival of their daughter on Saturday 18th September 2021, at 23.42, at the Chelsea and Westminster Hospital, London," the palace shared. "The baby weighs 6 pounds and 2 ounces. The new baby’s grandparents and great-grandparents have all been informed and are delighted with the news."
"The family would like to thank all the staff at the hospital for their wonderful care. Her Royal Highness and her child are both doing well, and the couple are looking forward to introducing their daughter to her big brother Christopher Woolf," the statement continued.