All the latest on the world's youngest royals
It's said that when Prince William was seven years old, he told his mother he wanted to be a policeman when he grew up.
"Oh no you can't," his younger brother Harry responded. "You've got to be King."
At a very tender age, Prince Charles and Diana's eldest son carried a big weight on his little shoulders.
But with his parents' commitment to give their boys a 'normal' upbringing, William was able to enjoy a relatively conventional childhood – despite the trappings of his royal position.
It's an approach he will no doubt be keen to take with his own children as he and Kate attempt to raise their family under the watchful eye of the media.
Like William, the new arrival, who will make his or her arrival in 2013, will grow up in Kensington Palace.
William was raised in Apartments 8 and 9, which were combined in 1981 to create Charles and Diana's London residence – she remained there after their divorce in 1996 until her death a year later.
The Cambridges, meanwhile, have decided to take the former home of the Queen's sister, Princess Margaret, as their permanent base in the capital.
Apartment 1A boasts four stories, six bedrooms and a private walled garden – plenty of space for their little ones to run around.
As busy working royals, the couple will need outside help when it comes to childcare.
It's a concept familiar to William. His childhood nanny Barbara Barnes, whom he affectionately called Baba, was instrumental in his upbringing and remains very dear to him – hers was one of the most important names on the guest list at the couple's glittering wedding.
And his wife may well choose to take a leaf out of Princess Mary's book.
The hands-on Danish royal recently revealed that she and Frederik only use nannies when they leave the house, preferring to look after their four children on their own while at home.
Once their little ones get a bit older, the Duke and Duchess are likely to make use of the local schools.
Both William and Harry attended Mrs Jane Mynor’s Nursery in west London, located three minutes from the Palace, before progressing to Wetherby School, a local boys pre-preparatory.
Princess Diana was often seen dropping the young princes off at Wetherby, and it was there that she famously won a race on sports day in 1989.
That kind of hands-on attitude is likely one that will appeal to both Kate and William.
And by sending their children to school, they will be continuing a tradition started by Charles, the first heir to the throne to be educated alongside his peers rather than by private tutors.
William's father was also something of a pioneer when it came to his family’s privacy.
Determined to juggle public interest with a paternal desire to protect his sons, he struck a deal with the press whereby William and Harry were left alone during their time at school in return for limited access at press and photo calls.
It was a decision that worked well for the Windsor boys, allowing them to grow and develop in a safe and private environment.
It may well be that William and Kate follow suit.
Already two of the most photographed people in the world, they deal with media intrusion to an even greater extent than William's parents did. And there will be huge interest in their children as the next generation of British royals.
They face a difficult balancing act letting their little ones enjoy a carefree, happy childhood while still understanding their extraordinary birthright.
It was an equilibrium the Princess of Wales worked hard to find.
Diana's former secretary, Patrick Jephson, says she repeatedly told her eldest he had been born to fulfill a duty, and that it would be an opportunity for him to use his influence for the good of those less fortunate than himself.
It's a message instilled in William, who, along with Harry, is a dedicated charity campaigner - already patrons of numerous endeavours, the brothers took the step of setting up their own foundation together in September 2009.
And in an interview for his 21st birthday, William clearly stated: "All these questions about do you want to be king. It's not a question of wanting to be, it's something I was born into and it's my duty."
While ensuring her sons understood the privilege of their position, Diana also worked tirelessly to bring a sense of normalcy to their extraordinary lives.
As well as taking her boys along to AIDS clinics and homeless shelters, she took them for trips to theme parks and fast food restaurants and bought them video games to play.
She was also hugely affectionate – the people's princess was first and foremost a devoted mother who took the attitude that "Hugs can do great amounts of good – especially for children."
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All the latest on the world's youngest royals