Prince Charles has the privilege of changing his name when he becomes the monarch after Queen Elizabeth and he might just go with King Philip as his regnal name as a tribute to his father, the Duke of Edinburgh.
According to reports, Charles was said to have told close friends that he will drop his given first name and opt to use one of his three other names when he becomes the King of the United Kingdom. The Prince of Wales was christened Charles Philip Arthur George in 1949.
Initially, however, the future king wanted to go by King George VII as his regnal name after his grandfather, King George VI. He felt that this was also a fitting tribute to his grandmother, the Queen Mother, who was devoted both to her husband and her first-born grandson.
It has long been a practice for monarchs to change names when they take the throne. For instance, Albert was the given first name of the queen's father. However, he decided to use one of his middle names (Frederick Arthur George) as his regnal name to follow after his own father, King George V.
Queen Victoria, one of the longest-reigning monarchs of Britain and the great-great-great-grandmother of both the queen and the Duke of Edinburgh, was christened as Alexandra Victoria. According to historians, she picked her second name as her regnal name because she thought it sounded more elegant than her first name or her nickname "Drina." Her heir and successor, King Edward VII, was named Albert Edward at birth but he also chose a different regnal name because he thought the name "Albert," after his father, "should stand alone."
When Queen Elizabeth became the monarch, she was asked what regnal name she'll use. However, she didn't have to change anything because she has always thought Elizabeth was the perfect one for her. The queen is actually christened Elizabeth Alexandra Mary.
Meanwhile, when Charles becomes the king then he could also change their family's surname if he wants to. Queen Elizabeth picked Windsor for their house and surname to follow the wishes of his father and then later issued a decree to also allow the royal family to use "Mountbatten-Windsor" to include her husband's roots.
Thus, some of the non-titled and extended members of the royal family either use Windsor or Mountbatten-Windsor as their surname. Some examples of these are Lady Louise Windsor, the daughter of Prince Edward and Sophie, the Countess of Wessex, or Archie Harrison Mountbatten-Windsor, the grandson of Prince Charles via Prince Harry and Meghan Markle.
