Mark Cuthbert/UK Press via Getty Princess Beatrice
Princess Beatrice is the proud mom of a "little rockstar."
Italian royal fan Jessica, who documents her interactions with royal families around the world by mail on her Instagram page RoyalAddicted_Replies, shared a handwritten note from Princess Beatrice that she received after congratulating Queen Elizabeth's granddaughter on the birth of her daughter Sienna Elizabeth in September.
On the back of the card featuring Sienna's footprints against a pink background, Beatrice wrote, "Thank you so much for thinking of us at this remarkable and special time."
"We are so thankful to have welcomed this little person into our family," she continued. "She is a little rockstar!"
Princess Beatrice, 33, signed the note from herself, "Edo" (the nickname for her husband Edoardo Mapelli Mozzi, "Wolfie" (the nickname for Beatrice's stepson Christopher Woolf from Edo's previous relationship with Dara Huang) and Sienna.
The envelope has stamps of Queen Elizabeth's initials and Buckingham Palace as well as a "Royal Mail" label.
The royal mom has already updated her accessory collection to include a tribute to her family. In a photo taken last month, Beatrice wears a necklace featuring the first initials for Sienna, Edo and Wolfie.
"We are all doing well and Wolfie is the best big brother to Sienna," they said in the statement.
Chris Jackson/Getty Princess Beatrice and Edoardo Mapelli Mozzi
About a month after her birth, Sienna was added to the line of succession to the throne on the royal family's official website. She is listed at the 11th spot, just behind her mother, as "Miss Sienna Mapelli Mozzi."