Princess Beatrice.Photo: Mark Cuthbert/UK Press via Getty

Princess Beatrice d’York

Princess Beatriceis the proud mom of a “little rockstar.”

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 husbandEdoardo Mapelli Mozzi, “Wolfie” (the nickname for Beatrice’s stepson Christopher Woolf from Edo’s previous relationship withDara Huang) and Sienna.

The envelope has stamps ofQueen 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, Beatricewears a necklacefeaturing the first initials for Sienna, Edo and Wolfie.

Princess Beatricesaid last year thatbecoming a stepmom was a “great honor,“and the couple included him when theypublicly announced their daughter’s name.

“We are all doing well and Wolfie is the best big brother to Sienna,” they said in thestatement.

Princess Beatrice and Edoardo Mapelli Mozzi.Chris Jackson/Getty

princess beatrice

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About a month after her birth, Sienna wasadded to the line of succession to the throneon the royal family’s official website. She is listed at the11th spot, just behind her mother, as “Miss Sienna Mapelli Mozzi.”

source: people.com