Congratulations are in order for Princess Eugenie and her husband, Jack Brooksbank, who welcomed their baby daughter on Monday night at a hospital in London. The proud mother announced the happy news on social media, sharing a photo of their newborn and a caption that read: "Jack and I are so excited to announce Baby Girl Brooksbank!! We are beyond in love with our girlie."

Eugenie and Jack have not yet revealed their daughter's name, fueling speculation about their choice. While the first name remains a secret, the baby's middle name is more predictable given her royal lineage. It is highly probable that Eugenie's baby will be given the middle name Elizabeth, in honor of her great-grandmother, the late Queen Elizabeth II. This follows a long-held tradition for modern royals, with Elizabeth's daughter, granddaughters, and great-granddaughters often bearing her name.

For example, Queen Elizabeth II was born Anne Elizabeth Alice Louise, and she named her daughter Anne. Eugenie's sister, Princess Beatrice, was born Beatrice Elizabeth Mary, and she gave the middle name Elizabeth to both of her daughters, Sienna Elizabeth Mapelli Mozzi and August Elizabeth Brooksbank. Prince Edward's daughter and Elizabeth's youngest grandchild, Lady Louise Alice Elizabeth Mary Mountbatten-Windsor, also carries the name. Furthermore, five out of seven of the late queen's eight great-granddaughters were given her name, including Sienna, Athena, Isla Elizabeth Phillips, Lena Elizabeth Tindall, and Lilibet Diana Mountbatten-Windsor.

Interestingly, Prince Harry's daughter, Lilibet, was given Elizabeth's childhood nickname rather than her direct moniker. Since her older sister already had the middle name Elizabeth, Eugenie herself was named after another great queen, with her full name being Princess Eugenie Victoria Helena.

Eugenie and Jack have a history of honoring family members with their sons' names. Their first son, August Philip Hawke, was named to honor both royal and common family members. August is a nod to Queen Victoria's husband, Prince Albert, who was born Prince Franz August Karl Albert Emanuel. Philip honors Eugenie's grandfather, Prince Philip, Duke of Edinburgh. Eugenie stated in the documentary Prince Philip: The Royal Family Members, "We named August, August Philip, because grandpa has been such a huge, inspiring character in my life." The moniker Hawke was inspired by Jack's family member, Rev. Edward Hawke Brooksbank.

Their second son, Ernest George Ronnie, was named for his great-great-great-grandfather, King George V, whose full name was George Frederick Ernest Albert. Jack's father was also named George, while Ronnie is in honor of Eugenie's maternal grandfather, Major Ronald Ferguson. Eugenie's mother, Sarah Ferguson, shared on a podcast, "When Jack and Eugenie told me, it was so moving that they put my dad in there. It was very kind, I thought. Yeah, made me cry, of course."

By not immediately revealing their baby girl's name, Eugenie and Jack have deviated from their previous patterns. August's name was withheld for 11 days, while Ernest's name was announced immediately with his birth. The royal, 36, and her husband Jack Brooksbank, 40, have welcomed a baby daughter, a younger sister for August, five, and Ernest, three.