Despite being Princesses by birth, Beatrice and Eugenie did not wear a tiara until their respective wedding days.
Eugenie was loaned the Greville Emerald Kokoshnik tiara for her marriage to Jack Brooksbank in October 2018.
Like her cousins, Lady Louise is likely to make her tiara debut when she marries.
And she has a few jewels worn by her mother, Sophie, that she could choose from.
When the former PR boss married Prince Edward in 1999, Sophie was gifted the Anthemion tiara, which is known to be made up of a number of antique pieces from the late Queen Elizabeth II's collection. The headpiece is Sophie's signature tiara and recently underwent a redesign.
The Duchess also has an aquamarine tiara which can be converted to a necklace. It is believed to be part of her own personal collection.
Sophie has also frequently worn the late Queen's Five Aquamarine tiara.
Princess Anne is one of the few royals to have worn a tiara before marriage. Royal ladies used to often wear jewels to film premieres and balls.
However, in modern times, tiaras are usually reserved for state banquets, the annual Diplomatic Corps reception and the State Opening of Parliament.
It was the first time the diamond headpiece had been seen in over two decades. Beatrice's mother, Sarah, Duchess of York was gifted it for her marriage to Prince Andrew in 1986 by her in-law, the late Queen Elizabeth and the late Duke of Edinburgh.
Lady Louise, who recently passed her driving test and is currently studying English at the University of St Andrews, is not expected to become a full-time working royal once she has completed her education.
Speaking to The Sunday Times in 2020, the Duchess spoke about the futures of Lady Louise and her younger brother, James, Earl of Wessex: "We try to bring them up with the understanding they are very likely to have to work for a living. Hence we made the decision not to use HRH titles. They have them and can decide to use them from 18, but I think it's highly unlikely."