The new royal baby has been born into a life of great privilege.
Despite the wealth and palaces, however, the life of a senior royal is not always easy and can - according to royal watchers - be a lonely one.
There are few people who are able to understand what it means to occupy such a high-profile position.
For a future heir like Prince George, the new princess may be the only one who truly can.
The Queen had a famously close relationship with her younger sister, Margaret.
The two had little option but to get on as young girls as they had little contact with the outside world.
Both were home-schooled and a guide troop was even set up in Buckingham Palace to allow them some contact with their peers, but within the confines of the palace.
The sisterly bond continued throughout their lives. Despite being very different in character they were a tight unit, reportedly telephoning each other every day.
Prince Charles and Princess Anne are 21 months apart - the same as Prince George and his new sister.
A private letter written by the Queen, then Princess Elizabeth, when Anne was just three weeks old described Charles as being "fascinated by her" and said he treated her "with great care".
However, despite the fact that as adults they have chosen country homes less than 10 miles apart, they have not been seen as particularly close, although they do get on well.
Royal siblings have had tricky relationships over the years.
One of the most dramatic falling outs came in 1478, when Edward IV reportedly had his younger brother George, Duke of Clarence - suspected of treason - drowned in a butt of wine.
Such sibling rivalry is in direct contrast to Prince George's father and uncle who continue to enjoy a very close relationship.
As well as having to grow up in public, William and Harry had to cope with the death of their mother when they were just 15 and 12, and the brothers have spoken about how they are the other's best friends.
Penny Junor, who has profiled both the princes, says being a royal child is difficult.
"They will always be an object of curiosity", she says, adding that having a close sibling was "certainly invaluable for William and Harry when they were growing up and still is today and will be for George and his little chum".
Princess Diana tried to make William and Harry's upbringing as normal as possible, and this is clearly a priority for the Cambridges.
The downside for a public keen to see George and his sibling is that much of their growing up will be done behind closed doors.
Prince George has been an object of global fascination since his birth in July 2013.
However, the media have had few opportunities to film him: the first view on the steps of the Lindo wing, his christening and when he accompanied his parents on their tour of Australia and New Zealand in April last year.
Photographs have been released to mark key moments including his first birthday, and each time his clothes, appearance and demeanour have been scrutinised, commented upon and copied.
Now there are two royal youngsters there will be double the interest.
But they can at least share the intense spotlight which will be trained upon them throughout their lives.