The succession to the British throne “is regulated not only through descent but also by Parliamentary statute,” according to the Royal Family’s website.
Prince William and his wife Kate Middleton, the Duchess of Cambridge, recently changed the line of succession with the birth of their third child, Prince Louis, on April 23.
And Prince Harry and Meghan Markle are going to impact the line once again. The newlyweds announced in October they're expecting their first baby in the spring of 2019.
"Their royal highnesses have appreciated all of the support they have received from people around the world since their wedding in May and are delighted to be able to share this happy news with the public," Kensington Palace said in a statement.
When Markle gives birth, the newest royal baby will become seventh in line to the throne — behind his or her dad.
Here’s a look at who currently is in line for the throne after Queen Elizabeth II, who is 92.
1. The Prince of Wales
Charles, the Prince of Wales, is the oldest child of Queen Elizabeth II. He is 69 years old and the heir apparent to the throne.
2. The Duke of Cambridge
Prince William, the Duke of Cambridge, is the oldest son of Charles. The 35-year-old is second in line to the throne. He married Kate Middleton in 2011.
3. Prince George of Cambridge
At only 4 years old, Prince George of Cambridge is third in line of succession to the British throne. He is the oldest child of Prince William.
4. Princess Charlotte of Cambridge
Princess Charlotte of Cambridge is the second child of Prince William and Kate, Duchess of Cambridge. She is 2 years old.
5. Prince Louis Arthur Charles of Cambridge
Kate Middleton and Prince William welcomed a baby boy on April 23, making him fifth in line to the throne.
He was named after William's grandfather, Prince Charles, and the Duke's mentor -- Louis Mountbatten -- who was killed by a bomb in 1979.
6. Prince Henry of Wales
Prince Henry of Wales – also referred to as Harry – is the sixth in line to the throne. He is the younger son of Charles, the Prince of Wales.
7. Duke of York
Prince Andrew, the Duke of York, is Queen Elizabeth II’s third child and second son. The 58-year-old is seventh in line of succession to the British throne.
8. Princess Beatrice of York
Princess Beatrice of York is Prince Andrew’s oldest daughter. She is 29 years old.
9. Princess Eugenie of York
At 28 years old, Princess Eugenie of York is the youngest daughter of Prince Andrew. She is ninth in line for the throne.
10. The Earl of Wessex
Prince Edward, the Earl of Wessex, is the third son of Queen Elizabeth II. The 54-year-old is her fourth child and 10th in line for the throne.
11. Viscount Severn
At 10 years old, James, the Viscount Severn, is the youngest grandchild of Queen Elizabeth II. He is the only son of Prince Edward.
12. The Lady Louise Mountbatten-Windsor
Lady Louise Mountbatten-Windsor is the oldest child of Prince Edward. Lady Louise, 14, is the granddaughter of Queen Elizabeth II.
13. The Princess Royal
Anne, the Princess Royal, is the only daughter of Queen Elizabeth II and her second child. At 67 years old, she is 13th in line of succession to the throne.
14. Mr. Peter Phillips
Peter Phillips, 40, is the only son and oldest child of Anne, Princess Royal.
15. Miss Savannah Philips
Savannah Ann Kathleen is the first child of Peter Phillips. The 7-year-old is also the first great-grandchild of Queen Elizabeth II.
16. Miss Isla Phillips
Isla Elizabeth Phillips, 6, is the daughter of Peter Phillips. She is 16th in line to the throne.
17. Mrs. Michael Tindall
Zara Tindall, 36, is the only daughter of Anne, Princess Royal. She is also Anne’s second child.
The Associated Press contributed to this report.