Prince William and Kate Middleton have already changed their titles on Instagram.
Queen Elizabeth II may have only just passed but a change of power is already in effect. With Prince Charles assuming the role of King and Prince William and Kate Middleton moving up in rank, ET's royal expert, Katie Nicholl explains all the title changes expected amongst the royal in the wake of the Queen's death.
"Within minutes of Buckingham Palace addressing the very sad news of the Queen's passing, we heard the first words from the new King and confirmation from Buckingham Palace that Charles will indeed be known as King Charles III," Nicholls said. "He could've chosen to take a different name as King. He has chosen King Charles III."
Camilla Parker Bowles, meanwhile, will go from Duchess of Cornwall to Queen Consort.
The title of Queen Consort was one Queen Elizabeth said she wished for Camila to take upon her passing.
"What we do know about the titles, is that King Charles has decided to be King Charles III, and we do know that we now have Queen Consort Camilla," she explained. Of course, the Queen used that anniversary of her accession for her 70th to make it known that it was her expressed wish for Camilla to become Queen Consort the moment the Queen's heart stopped beating. Charles became King Charles, Camilla became Queen Consort.
William and Kate Middleton have already changed their titles on Instagram, going from the Duke and Duchess of Cambridge to the Duke and Duchess of Cornwall and Cambridge. They will next take on the title of Prince and Princess of Wales.
"It is more likely than not that Prince William, the Duke of Cambridge will become the Prince of Wales, and Catherine, in turn, the Princess of Wales," Nicholls shared. "They will also inherit a number of titles through Charles, who will relinquish the Prince of Wales title now that he is King Charles III."
The Princess of Wales title was previously held by Princess Diana, and while many comparisons have been made between the late princess and Kate, Nicholls said Kate has successfully created a "new role for herself" separate from Diana, despite having big shoes to fill.
"There have been inevitable comparisons between Catherine and the Princess of Wales ever since she got engaged to Prince William," she added. "I think one of the Duchess of Cambridge's greatest successes has been creating a new role for herself away from the shadows of Princess Diana, but of course, she was always going to inherit the title Princess of Wales, and of course, and she more than anyone will know that they are sizable shoes to fill.
On Thursday, Buckingham Palace announced that Queen Elizabeth II -- the United Kingdom's longest-reigning monarch -- had passed at the age of 96.
"The Queen died peacefully at Balmoral this afternoon," the palace's statement read. "The King and The Queen Consort will remain at Balmoral this evening and will return to London tomorrow."
Concern over Her Majesty's health began Thursday morning when Buckingham Palace announced, "Following further evaluation this morning, The Queen’s doctors are concerned for Her Majesty’s health and have recommended she remain under medical supervision."
The queen's family, including her four children, King Charles, Princess Anne, Prince Andrew, Duke of York, and Prince Edward, Earl of Wessex, grandchildren Prince William and Prince Harry, and several other members of the royal family, all traveled to Balmoral Castle in Scotland amid the news of her declining health.
Her Majesty is survived by her children, along with eight grandchildren and 12 great-grandchildren.
For updates on Queen Elizabeth's death, visit ET's ongoing coverage and see more below.