In modern royal memory, the "spare to the heir" has often struggled to find their place in the world behind their throne-bound elder sibling.
But the Duchess of Cambridge is determined that history will not repeat for her second-born child, six-year-old Princess Charlotte.
"It's an all-too painful fact for the royal family that the Queen's sister Princess Margaret was – and future King William's brother Prince Harry is – miserable in their second-in-command roles, that are relegated as soon as the monarch [Elizabeth or indeed William] had a child of their own," says a source.
"Kate doesn't want this pain for Charlotte – she doesn't want her confident, gregarious daughter to feel she has to dull herself so as not to outshine her big brother [Prince George]."
The insider tells Woman's Day that Kate is "strategically" planning for Charlotte and eight-year-old George's teenage years, when they'll both be expected to undertake more royal appearances.
"As soon as they're old enough, Kate wants them to work in tandem rather than George getting the pick of events," says a source.
"In the meantime, Kate's keen to impress on Charlotte how important she is as part of the royal makeup, and make sure she has keen interests to promote on her own terms.
"That's why you're seeing Kate putting Charlotte front and centre for the butterfly charity photo op – something George could have easily done, but the Cambridge kids will share the load equally as they grow up.
"Kate's worst nightmare is seeing Charlotte miserable enough to ditch the family like Harry has done."