Big celebration to the Royal family: Meghan Markle and Prince Harry Celebrate Princess Lilibet’s 3rd Birthday with Party at Montecito Home

The birth announcement also referred to the newborn as Lili, a nickname that Prince Harry and Meghan have continued to call their daughter.

In March 2023, PEOPLE exclusively revealed that the Duke and Duchess of Sussex were using their children’s royal titles through the news of their daughter’s christening announcement. Once their grandfather King Charles acceded to the throne in September 2022, Archie and Lilibet were afforded the titles of prince and princess, making them Prince Archie and Princess Lilibet.

The royal family’s official website was updated to reflect the children’s new titles the next day, and the children are referred to by their royal titles in their parents’ biographies on sussex.com, which launched in February. Around the same time, PEOPLE learned that Prince Harry, 39, and Meghan, 42, have adopted their titles of the Duke and Duchess of Sussex as the last name for their children. PEOPLE understands that Sussex is their family surname. Using their titles as their children’s last names follows the tradition historically used by members of the royal family.

The Duke and Duchess of Sussex will mark the third birthday of their daughter, Princess Lilibet, but they got the festivities started early with pre-birthday bash. The family celebrated over the weekend with a party at home in Montecito, California, PEOPLE confirms. Among the guests were close friends and family as well as some of Lili’s friends.

Lilibet Diana Mountbatten-Windsor was born in California after Prince Harry and Meghan stepped back from their royal roles and moved to Meghan’s home state in the U.S. with their son, Prince Archie, now 5, in 2020. Lilibet’s birth announcement, shared on the Archewell Foundation website, said that she was named after Queen Elizabeth’s family nickname while her middle name, Diana, “was chosen to honor her beloved late grandmother, the Princess of Wales.”