Prince William and Kate's baby boy is the third in line to the British throne.
Here is a factbox on how the position of third in line has changed hands since the birth of Queen Elizabeth II in 1926.
Births, deaths and abdication have nudged senior royals up and down the list.
Queen Elizabeth's late sister Princess Margaret, her daughter Princess Anne, and her uncle Prince Henry had repeated turns in the position.
Through twists of fortune, some go on to inherit the throne, while others slide ever further down the order.
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Third in line can prove a tricky place to be, bearing the burdens of being close to the throne but without a specific role to fulfil.
ELIZABETH, 1926-1936
In the reign of her grandfather King George V, Princess Elizabeth of York was born third in line after her uncle, the future king Edward VIII, and her father, Prince Albert of York, nudging her uncle Prince Henry down a place. She was not thought likely to inherit the throne, with Edward still unmarried.
MARGARET, 1936-1936
When King George V died in 1936, Elizabeth's sister, Princess Margaret of York, moved up to third. However, by the end of the year, she moved up again to second when the new king, Edward VIII, abdicated in order to marry US double-divorcee Wallis Simpson.
HENRY, 1936-1948
The abdication propelled Albert onto the throne as king George VI, leaving his younger brother Prince Henry third in line for the next 12 years, behind the new monarch's daughters Elizabeth and Margaret.
MARGARET, 1948-1950
When Elizabeth's first child Prince Charles was born second in line, that pushed Margaret back down into third place.
ANNE, 1950-1952
Elizabeth's second child, Princess Anne, was born third in line to the throne behind her mother and Charles.
MARGARET, 1952-1960
However, the death of King George VI in 1952 saw everyone move up one place as Elizabeth became queen, meaning Margaret saw out the 1950s third in line again.
ANNE, 1960-1964
Anne was pushed back down into third place when her younger brother Prince Andrew was born, with male children overtaking their older sisters in the line of succession. This law is now being changed, so the new baby could not be usurped if it were a girl.
EDWARD, 1964-1982
When a second younger brother Prince Edward was born in 1964, he, too, immediately overtook Anne, pushing her further back. The new baby will make her 11th in line.
ANDREW, 1982-1984
Edward stayed third in line for 18 years until Charles' eldest son William was born in 1982, pushing Andrew briefly back down to third.
HARRY, 1984-2013
Two years later, Charles's second son Prince Harry was born third in line behind William and his father.
WILLIAM'S BABY SON, 2013 -
William's baby son, his first child, is third in line to the throne, overtaking Harry.
