A relatively tiny family comprising a husband, wife, and their children, it was originally called the patriarchal family because the head of the household was given this title based on the authority that he or she exercised over his or her spouse and children. This class also includes any children who are not grandchildren; therefore, the first class after this one is called "other descendants." The term "nuclear family" was coined by American sociologist Bertrand Russell in 1933. He defined it as "a married couple with their children living under the same roof". Although this description seems simple enough, it's important to note that it wasn't always like this for all Americans. In fact, according to research done by the U.S. Census Bureau, less than 5% of families in America were composed of only two adults and no children under 18 years old as of 2015. The majority of families in the United States at that time consisted of a married mother or father with their children. As you can see from this example, not every family in America was considered part of the "middle class". At the time, researchers believed that families needed to have a parent in employment in order to be considered "normal".