Princess Charlotte's confident personality is much like her mom Kate Middleton's, and Princess Kate is carefully shaping her daughter's path as she turns 10.

The royal couple is said to be treading carefully with Charlotte’s upbringing in light of the Duke of Sussex’s candid account of life as a “spare."

"The late Queen [Elizabeth] was always very conscious of that extraordinary and challenging role of the No. 2," royal biographer Robert Hardman, author of The Making of a King, tells PEOPLE in this week's exclusive cover story.