His Royal Highness Prince Philip died Friday morning at the age of 99, Buckingham Palace announced (opens in new tab). It is with deep sadness that Her Majesty the Queen announces the passing of her beloved husband, His Royal Highness Prince Philip, Duke of Edinburgh." His Royal Highness breathed his last peacefully this morning at Windsor Castle."

Philip married the then Princess Elizabeth in 1947, five years before she became queen, and was subsequently created Duke of Edinburgh, Earl of Merioneth, and Baron of Greenwich, Harper's Bazaar reports (opens in new tab). He also had to renounce his previous royal titles of Prince of Greece and Denmark in order to marry Elizabeth. However, he did not become king upon his wife's accession to the throne, nor did he become Prince Philip immediately after marrying the princess. Instead, the Queen made Philip Prince of England by letter patent in 1957, the year of their tenth wedding anniversary.

So why didn't Philip become King? The spouse of an English monarch is called a queen, and while a king's wife is usually given the title of "queen consort," the queen's husband has never been a queen of a king. Queen Victoria created the title Prince Consort for her husband Prince Albert, but Philip, the only male consort since Albert, is officially called Prince of the United Kingdom instead. According to Town & Country magazine (opens in new tab), this convention stems from the ancient royal patriarchy, in which the king must be the ruler, but the queen must be only a symbolic figure. [Prince Charles' wife Camilla Parker Bowles (formally Camilla, Duchess of Cornwall) was customarily the queen when Prince Charles became king. However, prior to their marriage in 2005, the Palace announced that she would become Princess Consort upon Prince Charles' coronation, perhaps to avoid further controversy (opens in new tab) following the collapse of his marriage to Princess Diana. Harper's Bazaar reports (opens in new tab) that "Mrs. Parker Bowles will use the title Princess Consort when the Prince of Wales ascends to the throne," Clarence House said in a statement.

As Town & Country reports, the royal family has made no such statement regarding Kate Middleton, who married future King Prince William in 2011 (opens in new tab). Thus, for now, it is safe to assume that she will receive the title of queen and be known as Princess Catherine.