With Prince George set to be King one day and Princess Charlotte third-in-line to the throne, there is more freedom for Louis to express himself, the expert said.
The psychologist told OK! magazine: “By the third child, you’re much more adept and confident as a parent and that really shows.
“You’ve got this little boy whose older brother will one day be King, so he’s never going to be anything but the underdog and I think Kate, more than anybody, will be aware of that.
“I love the way she smiles and allows Louis to just be himself. That’s really important.”
Over the Coronation weekend Louis once again delighted royal fans with his antics, as he pulled his trademark faces on the Buckingham Palace balcony after the ceremony.
On Monday May 8 he joined the rest of his family to take part in the Big Help Out by volunteering at the 3rd Upton Scout Hut in Slough.
As a reward for his hard work he was seen happily tucking into some s’mores with the rest of the helpers.
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King Charles has long expressed his wish for a slimmed-down monarchy, however there may soon be a gap in the number of royals available for engagements as some look to retire.
Mr Fitzwilliams added: “Of course George and Charlotte and Louis played a role of one sort or another in the different days in the during the Coronation weekend.
“I mean it was wonderful to see George as a page of honour, but it is obviously going to be a long time before any of them are able to participate in royal engagements actively.
“And this does mean that, firstly, The Waleses are the future of the monarchy, there’s absolutely no doubt about it.
“But secondly, who’s going to take up all these hundreds of patronages at the moment which are at the moment vacant?”
