The exposure weighed heavily on them and affected them both mentally, Prince Harry revealed at a later date.
Charlotte, 3, was dressed in a blue floral frock, wearing her hair parted in the middle the princess wore a blue headband that had a bow attached at the top.
If the moniker sounds familiar, you should know that it previously belonged to the late Princess Diana. Instead, it is the Queen's busy schedule that kept her away from the event, but her absence was a mutual decision between the monarch, Prince William, and Kate Middleton.
Nevertheless, only time will tell.
Louis was baptised by the Archbishop of Canterbury, the Most Reverend Justin Welby in a 40-minute service which started at 4 pm, and was attended by royals including William's brother Prince Harry and his new wife Meghan, Duchess of Sussex.
Older brother Prince George walked in holding Prince William's other hand, while Duchess Kate carried their baby brother in his heirloom lace christening gown.
The christening of Prince Louis was held in the Chapel Royal at London's St James's Palace on Monday afternoon and the royal family looked in great spirits - and totally stylish - for the special event.
The final guests were the young prince's six godparents and their spouses, all of whom are friends or family of the Duke and Duchess.
Kate's younger sister Pippa Middleton and her husband, James Matthews were also present.
While it was widely reported that the 36-year-old recycled the look from her daughter's christening at Prince Harry and Meghan's wedding in May, eagle-eyed fans noted subtle differences.
But although the ceremony might have been a snooze for a tiny prince, the fashion from the day wasn't.
Prince Louis' christening was the first time that the Duke and Duchess of Cambridge made a public appearance with all of their children.