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2018 has been a big year for the extended royal family, with two new babies and two weddings already. Read on to see how all these events affect the line of succession.
WHO IS NEXT IN LINE?
Until the baby is born, here are the first 10:
1. Charles, Prince of Wales - The queen's firstborn
2. William, Duke of Cambridge - Prince Charles' firstborn and the queen's grandchild
3. Prince George of Cambridge - Prince William's firstborn and the queen's great-grandchild
4. Princess Charlotte of Cambridge - Prince William's second child and the queen's great-grandchild
5. Prince Louis - Prince William's third child and the queen's great-grandchild
6. Prince Henry (Harry) of Wales - Prince Charles' second child and the queen's grandchild
7. Andrew, Duke of York - the queen's third child and second eldest son
8. Princess Beatrice of York - Prince Andrew's firstborn
9. Princess Eugenie of York - Prince Andrew's second child
10. Edward, Earl of Wessex - the queen's youngest child and third eldest son
HOW IS THE LINE DECIDED?
The line of succession is determined by descent and also by Parliamentary statute, according to the royal family's website. This was decided by the Act of Settlement of 1701, which states that those in line to the throne must be protestant descendants of Princess Sophia. It was decided in the 2013 Succession to the Crown Act that those who marry Roman Catholics are no longer disqualified from the line.
The eldest son of the queen, followed by all his descendants, are in line for the throne ahead of all others. They are followed by her second eldest son and all his descendants, and so on.
HOW DOES GENDER PLAY A ROLE?
Though Anne, The Princess Royal, is Queen Elizabeth II's second-eldest child, she is 12th in line to the throne, behind her brothers and all their descendants. This is because the Act of Settlement of 1701 included a system of male primogeniture, which meant that younger brothers would jump in front of their older sisters in line.
This rule does not apply to the newest generation, however, thanks to the 2013 Succession to the Crown Act. It states that, for any royals born after Oct. 28, 2011, the succession will be decided by birth order, regardless of gender. Since Charlotte was born after this date, she will stay fourth in line even though she now has a younger brother.
WHAT EFFECT DID THE ROYAL WEDDINGS HAVE?
As you probably noticed, Kate, Duchess of Cambridge is not in line for the throne, even though her husband Prince William is second in line. Royal weddings do not immediately affect the line of succession because spouses are not descendants of Princess Sophia.
This means that neither Duchess Meghan (who married Prince Harry in May) nor Jack Brooksbank (who married Princess Eugenie in October) will be in the line. But what does that mean for any future children?
Meghan and Harry: Any children will be right after Harry in the line, in the order of their births. They will all be ahead of Prince Andrew.
Eugenie and Jack: Any children will be right after Eugenie in line, in the order of their births. They will be ahead of Prince Edward.
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WHAT EFFECT DID THE ROYAL BIRTHS HAVE?
William and Kate's child: Prince Louis is in line behind Prince George and Princess Charlotte, making him fifth. This has bumped everyone down one spot, making Prince Harry sixth.
Zara Tindall's child: Zara, a grandchild of Queen Elizabeth II, is the second child of Princess Anne. Zara and her husband already had one child, Mia Grace, who is 18th in line behind her mom. Zara's second child, Lena, was born in 2018 and is 19th in line.