Zara and Mike Tindall are set to welcome a new addition to their family when their third child arrives in 2021.
The couple are already parents to Mia, seven, and two-year-old Lena, and the siblings are set to benefit from an Act that was created thanks to their cousin Princess Charlotte, when the new baby is born.
If Zara gives birth to a son, Mia and Lena will retain their places in the line of succession. Mia is currently 19th in line, while her younger sister is 20th.
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Charlotte became the first female royal to benefit from The Succession to the Crown Act (2013), which states that girls will not be overtaken by younger brothers.
Mia and Lena will move further away from the throne when Princess Eugenie gives birth to her first child, but if they welcome a baby brother to the family, he won't overtake his older sisters in the line of succession.
And while the likes of Charlotte, Mia and Lena will benefit from this Act, other female royals have missed out on the change, as it only applies to those born after 28 October 2011.
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Princess Charlotte made history when Prince Louis was born
The Queen and the Duke of Edinburgh's only daughter Princess Anne is much further down the line of succession than her younger brothers Prince Andrew and Prince Edward.
The Princess Royal is currently in 14th place behind her niece Lady Louise Windsor.
If the rules had been changed at the time of Anne's birth in 1950, her children Peter Phillips and Zara Tindall would be much closer to the throne than their cousins Princess Beatrice and Princess Eugenie, who are currently ninth and tenth.
The Earl and Countess of Wessex's daughter Lady Louise Windsor, 17, was also overtaken by her younger brother James, Viscount Severn in the line of succession after his birth in 2007. James is currently 12th in line, while Lady Louise is 13th.
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