The birth of Prince Harry and Meghan Markle's baby boy means a change to the British Royal Family's line of succession.
While Queen Elizabeth is the current monarch, she won't be forever and will be immediately followed by her son Charles, the Prince of Wales.
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His firstborn son, William, the Duke of Cambridge, is next in line followed by William's three children - George, Charlotte and Louis.
Due to changes decided in the Perth Agreement, which came into effect in March 2015, Prince William and Kate Middleton's daughter, Princess Charlotte, did not move down the line of succession after the birth of Louis.
The agreement means rules preferencing the male were replaced with absolute primogeniture, which means sex does not affect the line of succession.
If all those five died or decided to abdicate the throne, Prince Harry would become ruler, followed by his newborn son.
It's unlikely he will move down from seventh anytime soon, unless William and Kate have another baby.
That pushes the likes of Prince Andrew, Princess Beatrice, Princess Eugenie and Zara Tindall all down the line of succession and further away from the crown.
No name for the baby boy has been announced, but the world likely get their first look at the child in the next two days.