A royal family is the extended family of a king or queen regnant. The term imperial family appropriately describes the extended family of an emperor or empress, while the terms "ducal family", "grand ducal family" or "princely family" are more appropriate to describe the relatives of a reigning duke, grand duke, or prince. However, in common parlance members of any family which reigns by hereditary right are often referred to as royalty or "royals".
Members of a royal family
A royal family typically includes the spouse of the reigning monarch, surviving spouses of a deceased monarch, the children, grandchildren, brothers, sisters, and cousins of the reigning monarch, as well as their spouses. In some cases, royal family membership may extend to great grandchildren and more distant descendants of a monarch. In certain monarchies where voluntary abdication is the norm, such as the Netherlands, a royal family may also include one or more former monarchs. There is often a distinction between persons of the blood royal and those that marry into the royal family. In certain instances, such as in Canada, the royal family is defined by who holds the styles Majesty and Royal Highness. Under most systems, only persons in the first category are dynasts, that is, potential successors to the throne (unless the member of the latter category is also in line to the throne in their own right, a frequent occurrence in royal families which frequently intermarry). The precise functions of a royal family vary depending on whether the polity in question is an absolute monarchy, a constitutional monarchy, or somewhere in between. In most constitutional monarchies, however, members of a royal family perform certain public, social, or ceremonial functions, but refrain from any involvement in electoral politics or the actual governance of the country.
The specific composition of royal families varies from country to country, as do the titles and royal and noble styles held by members of the family. The composition of the royal family may be regulated by statute enacted by the legislature (e.g. Spain, the Netherlands, and Japan since 1947), the Sovereign's prerogative and common law tradition (e.g. the United Kingdom), or a private house law (e.g., Liechtenstein, the former ruling houses of Bavaria, Prussia, Hanover, etc.). Public statutes, constitutional provisions, or conventions may also regulate the marriages, names, and personal titles of royal family members. The members of a royal family may or may not have a surname or dynastic name (see Royal House).
In a constitutional monarchy, when the monarch dies, there is always a law or tradition of succession to the throne that either specifies a formula for identifying the precise order of succession among family members in line to the throne or specifies a process by which a family member is chosen to inherit the crown. Some monarchies employ a mix of these selection processes (Malaysia, Monaco, Tonga, Jordan, Morocco), providing for both an identifiable line of succession as well as authority for the monarch, dynasty or other institution to alter the line in specific instances without changing the general law of succession.
Some countries have abolished royalty altogether, as in post-revolutionary France and Russia.