The wife of a king is also called a queen. However, the husband of a queen is not always called a king. For example, the last King of Britain (George VI) had a wife (Elizabeth), who was called Queen Elizabeth. He had no sons, so he was followed by his elder daughter, who is also called Elizabeth. She became Queen Elizabeth II. She was married to The Duke of Edinburgh until his death on April 9, 2021; but when she became Queen he did not become King.