While we know that the Queen was among the guests at the private family service at All Saints Chapel at Royal Lodge, Windsor, it has not been confirmed whether the tots wore the royal christening gown.
Given that it was a joint baptism, it's not known whether the royal mums had to do a quick swap of outfits so that both their sons could wear the gown, or whether they opted for different outfits entirely, in another break from tradition.
WATCH: British royal family's christenings through the years
Most royal christenings take place when babies are around three or four months old, and given that August and Lucas are nine and eight months respectively, they may have outgrown the gown already.
The royal christening gown is a replica of the original Spitalfields silk and Honiton lace one made in 1841 for Queen Victoria's eldest daughter. It was worn by 62 royal babies in total, including the current Queen.
Prince Louis wearing the christening gown in 2018
However, following the baptism of the Earl and Countess of Wessex's daughter, Lady Louise Windsor, on 24 April 2004, it was decided the garment was too delicate to be used again, so the monarch commissioned her dressmaker, Angela Kelly, to make an exact replica to replace the original robe.
Eugenie arriving at her son August's christening
The Wessexes' son, James, Viscount Severn, was the first royal baby to wear the replica gown at his christening in 2008. Since then, the likes of the Duke and Duchess of Cambridge's three children, Prince George, Princess Charlotte and Prince Louis, as well as the Duke and Duchess of Sussex's eldest child, Archie, have all worn the outfit to their baptisms.
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