This includes following style rules such as not wearing outfits that are too revealing or heels that are excessively high.
When Kate and Meghan have appeared to perform royal duties, all eyes are often on the pair to see what they are wearing, stylist Melita Latham explained.
She told Express.co.uk: “With Kate and Meghan, every inch of their ensemble is examined under the microscope that is the national press.
“Every fold, every button, considered and analysed.”
Both Duchesses have mixed designer pieces with high street outfits and are not afraid to rewear outfits.
No matter what they wear, the royals are sure to bring a lot of publicity to the brands and it has been speculated that they may have received items for free.
However, doing so is reportedly banned by the Royal Family which means Meghan and Kate have probably not worked with any brands.
Although they were not allowed to receive free items or benefit from brand collaborations, Melita explained this is something Zara Tindall has done.
Zara may be the eldest granddaughter of the Queen, but she has been allowed to receive items as she is not a working member of the family, the expert suggested.
She added: “As a non-serving royal, Zara can also accept gifts of clothes from designers, whilst the serving cannot.
“Although given the inherited wealth of all, it’s unlikely seen as a perk.”
Not having a senior royal role has also given Zara more freedom with her fashion choices.
“Whilst not a serving royal, at events she attends Zara gathers all the attention of a royal with very few of the drawbacks,” the expert commented.
“Her dress sense is – of all the royals – quite perfect.
“She can wear rather more daring, sometimes higher hemmed dresses, while also enjoying the casual slinky top and jeans. Her formal wear is exquisite yet relaxed.”