Royals 'Tween Queen' Princess Estelle of Sweden Turns 9 with Adorable New Photos! The family dog, Rio, and her little brother, Oscar, also made cameos By Stephanie Petit Stephanie Petit Stephanie Petit is a Royals Editor, Writer and Reporter at PEOPLE. People Editorial Guidelines Published on February 23, 2021 12:11PM EST Princess Estelle. Photo: Kate Gabor, The Royal Court of Sweden Princess Estelle of Sweden is a preteen queen-in-the-making! The palace marked Estelle's 9th birthday on Tuesday with the release of four new portraits. The princess looks more grown up than ever in the photos taken at Haga Castle outside Stockholm — where Estelle lives with her parents and 4-year-old brother, Prince Oscar — by Kate Gabor. In addition to three solo shots, Princess Estelle posed for a portrait with Prince Oscar and Rio, the family's Cavapoo (part poodle, part Cavalier King Charles Spaniel). The royal siblings are all smiles as the dog sits between them. Princess Estelle is the eldest child of Crown Princess Victoria and Prince Daniel, as well as the eldest grandchild of King Carl XVI Gustaf, making her second in line for the Swedish throne after her mother. Future Queens of Europe! Meet All the Female Heirs Set to Take the Throne Princess Estelle and Prince Oscar with Rio. Kate Gabor, The Royal Court of Sweden Princess Estelle. Kate Gabor, The Royal Court of Sweden Princess Estelle. Kate Gabor, The Royal Court of Sweden Even at her young age, Princess Estelle is preparing for her future role as monarch. In October, she joined mom Princess Victoria and grandfather King Carl Gustaf at the inauguration of the Golden Bridge in Stockholm. Princess Estelle, King Carl Gustaf and Princess Victoria. JONATHAN NACKSTRAND/AFP via Getty And the princess showed her excitement about the role over the summer by dressing in traditional costume to celebrate Nationaldagen (National Day) in Sweden alongside Prince Oscar. She was pictured wearing a traditional Swedish national dress — however, she is too young to wear the hat, known as a Sverigedräkten. The headscarf is only worn by Swedish princesses once they're married. Can't get enough of PEOPLE's Royals coverage? Sign up for our free Royals newsletter to get the latest updates on Kate Middleton, Meghan Markle and more! Just a few days ago, Princess Estelle's cousin Princess Leonore celebrated her 7th birthday in Miami. Leonore has lived in Florida since her mother, Princess Madeleine, and British-American father, Christopher O'Neill, relocated from Sweden in fall 2018.