The current royal line of succession includes immediate members of the Royal Family, such as grandchildren and great-grandchildren of the Queen.
Immediately due to succeed Queen Elizabeth II is The Prince of Wales (Charles), 72, followed by The Duke of Cambridge (William), 38, and then Prince George, 7.
The succession line also includes Zara Tindall, daughter of Princess Anne, who is married to former rugby player Mike Tindall.
However, what would the line of succession look like if Queen Elizabeth never had any children?
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The heir-apparent in this hypothetical line of succession would be the son of Princess Margaret, David Armstrong-Jones, 2nd Earl of Snowdon, 59.
He would be immediately followed by his son Charles Armstrong-Jones, 22, and his daughter Margarita, 19.
Who is the alternate heir-apparent?
David Armstrong-Jones, known as Viscount Linley until 2017, was born to Princess Margaret and her then husband Anthony Armstrong-Jones, Lord Snowdon.
As of December 2006, David has been the Chairman of Christie’s UK, a furniture company.
Prior to this, David set up his own furniture company, called David Linley furniture limited, which he lost after falling into some debt.
Other ventures of his include a restaurant, named Deals located in Chelsea, established with Patrick Lichfield, his second cousin.
Where does David Armstrong-Jones lie in the current line of succession?
David is currently 24th in line to succeed Queen Elizabeth II, behind of Lucas Philip Tindall, the five-month-old son of Zara and Mike Tindall, and ahead of his son, Charles Armstrong-Jones.
The Earl’s mum, Princess Margaret, died in 2002. The Queen has not neglected any of her family ties and remains close with the Earl.
Royal biographer Christopher Warwick gave an insight to this in the documentary ‘Princess Margaret: The Royal Rebel’.
He said: “Margaret and Tony had no compunction about going off on holiday and leaving the children behind.
“Very often, they were left in the care of the Queen – the Queen had David and Sarah, you know – and they loved it.”
He added: “Princess Margaret was a good mother, but more especially when the children were growing older. She wasn’t really the most maternal of women, so she wasn’t particularly interested in babies and toddlers.”