Zara and Mike Tindall will mark a new family milestone this month as their youngest child, Lucas, turns one on 21 March.
The couple are already parents to Mia, eight, and three-year-old Lena, and the siblings are set to benefit from an Act that was created thanks to their cousin, Princess Charlotte.
Although Zara welcomed her first son last year, Mia and Lena have retained their places in the line of succession. Mia is currently 22nd in line, while her younger sister is 23rd.
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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.
While Mia and Lena have moved further away from the throne due to the births of the Duchess of Sussex and Princess Beatrice's daughters last year, their baby brother Lucas hasn't overtaken his older sisters in the line of succession.
Similarly, if Princess Beatrice and Edoardo Mapelli Mozzi have a son in future, their daughter, Sienna, will remain above him in the line of succession.
And while the likes of Charlotte, Mia and Lena 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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© Photo: Getty ImagesPrincess Charlotte made history when Prince Louis was born
The Queen'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 17th 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 tenth and 12th.
The Earl and Countess of Wessex's daughter Lady Louise Windsor, 18, was also overtaken by her younger brother James, Viscount Severn, 14, in the line of succession after his birth in 2007. James is currently 15th in line, while Lady Louise is 16th.
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