THE Duchess of Cambridge gave birth on April 23, 2018, and the new royal baby boy's arrival was especially significant for little Princess Charlotte.
The three-year-old made history when her younger brother Prince Louis entered the world - and that down to the Succession to the Crown Act of 2013. Here are the details...
Why did Princess Charlotte make history?
Princess Charlotte became the first female royal to retain her claim to the throne, despite the having a younger brother.
Before the Succession to the Crown Act 2013 the birth of a son meant he would leap over any older daughters in the line of succession.
Therefore Princess Anne, despite being the Queen's second child, was in the line of succession beneath her younger brothers Andrew and Edward.
Princess Charlotte is the first royal not ruled out by gender, meaning that Prince Louis will be the fifth-in-line to the throne.
What are the rules of succession to the throne?
The Succession to the Crown Act 2013 means that a female royal’s claim to the throne is no longer diminished by the arrival of a younger brother.
It states: “In determining the succession to the Crown, the gender of a person born after 28 October 2011 does not give that person, or that person’s descendants, precedence over any other person (whenever born).”
Interestingly, as a result of the Act, had five-year-old Prince George been a girl, he still would have been next in line to the throne after his grandfather Prince Charles and dad Prince William - even if any younger siblings were boys.
Previously, the 1701 succession act stated that brothers would always come before their sisters when it came to who was first in line to the throne.
This year Prince Charles fuelled rumours that his wife Camilla Barker Bowles might become queen, after a statement saying she will become "Princess Consort" was removed from his website.
Meanwhile the Queen has more faith in Princes William and Harry than she does in son Charles, according to Andrew Morton’s book.
When did Kate give birth?
Kate Middleton gave birth to Prince Louis, on April 23, 2018.
Her husband Prince William was at her side.
The boy weighed 8lb, 7oz and is a brother for Prince George and Princess Charlotte.
MORE ON THE ROYAL BABY
Is Meghan Markle pregnant and where will her child fall in the line of succession?
Kensington Palace confirmed the news of the pregnancy on October 15, 2018.
The Palace also revealed that the baby is due in spring 2019 – but no exact date or month was given.
If Meghan is three months along, chances are the baby will be born in late March or early April.
The Duchess of Sussex’s baby will be a member of the Royal Family in its own right – as it will be the child of Prince Harry, the Duke of Sussex.
Prince Harry is the sixth in line to the throne – he is the son of Prince Charles, the Prince of Wales and the late Princess Diana.
Harry’s dad is the next in line to the British throne, while older brother William is the second.
The Sussex baby – regardless of its gender – will become the seventh in line to the British throne – bumping Prince Andrew, the Duke of York into eighth.