A royal house or royal dynasty consists of at least one, but usually more monarchs who are related to one another, as well as their non-reigning descendants and spouses. Monarchs of the same realm who are not related to one another are usually deemed to belong to different houses, and each house is designated by a name which distinguishes it from other houses. Strictly, a "royal house" is a dynasty whose members reign while bearing the title of king or queen, although it has become common to refer to any family which legally exercises sovereignty by hereditary right as a royal family, and its members as "royalty" or (colloquially) "royals". Historically, ruling families often consist of a senior and several junior branches, which are akin, but may have diverged in descent from a common ancestor many generations ago. The name used to refer to a royal house may or may not also be used by its members as a surname. Rather, members of dynasties are usually referred to by their titles, which may or may not also be hereditary.