Middle names are not usually used in everyday life. However, some people who are better known by their middle names may abbreviate their first given names to their initials. (e.g. F. Scott Fitzgerald and W. Somerset Maugham). Some people don't use first names at all (like Paul McCartney, whose first name is James).
In rare cases, a person may have a one-letter middle name that does not mean anything specific. (For example, U.S. President Harry S. Truman) This custom is more common among the Amish, who usually use the first letter of the mother's maiden name as the only middle name for their children.
Thus, Sarah Miller's children will use the middle name [M.]. The custom of abbreviating middle names to initials is relatively uncommon in the UK.
For example, Queen Elizabeth II Elizabeth Alexandra Mary (as a queen, she does not need a surname), J. R. R. Tolkien, George H. W. Bush and V. V. S. Laxman.
The British upper class traditionally like to use multiple middle names, such as William Arthur Philip Louis, Prince of Wales, Henry Charles Albert David, Prince Henry, or Anne Elizabeth Alice Louise, Princess Anne.
Extended information:
Usage in other places:
1. East Asia
Some Chinese names are single names (such as singer Wang Jay), naturally there is no middle name. Traditionally, there are several types of middle names in East Asia. One of the middle names of the Chinese names of China, Korea, Vietnam and Ryukyu is the character for generation, which has the function of distinguishing seniority. It also has the character for ranking, indicating the order of the family, but most of them are I no longer care about the meaning of the middle name, and have formed a single-character surname + a two-character first name.
Surnames were divided into surnames in ancient times. In addition, compound surnames, that is, double-character surnames, may also arise due to the history of the clan. In Vietnam and Ryukyu, the character "祧" is used to distinguish clans. Vietnam also has pad characters to distinguish gender. There are also some middle names in East Asian names that have no special meaning and are the first character of the given name.
2. Arabia
Arabs in the Middle East (especially the Levant) usually have two middle names: their father's given name, and then their grandfather's given name. In particular, some Arabs or Arab ancestors living in Western countries continue this practice.
It is customary for some Arabs (especially Syrians) to place a special name before the given name. However, this special name is not in the middle of the full name, but a prefix, but it has the same function as the middle name.
This name is generally regarded as a blessing, and is often the name Mohammad. For example, a person might be named Mohammad Hadi or Mohammed Basheer, but Hadi and Basheer are the middle names that are usually given by that person.
Baidu Encyclopedia-Middle Name