Heir apparent

Daughters (and their lines) may inherit titles that descend according to male-preference primogeniture, but only in default of sons (and their heirs). That is, both female and male offspring have the right to a place somewhere in the order of succession, but when it comes to what that place is, a female will rank behind her brothers regardless of their ages or her age.

Thus, normally, even an only daughter will not be heir apparent, since at any time a brother might be born who, though younger, would assume that position. Hence, she is an heir presumptive. For example, Queen Elizabeth II was heir presumptive during the reign of her father, King George VI, because at any stage up to his death, George could have fathered a legitimate son.

In a system of absolute primogeniture that disregards gender, female heirs apparent occur. As succession to titles, positions, or offices in the past most often favoured males, females considered to be an heir apparent were rare. Absolute primogeniture was not practised by any modern monarchy for succession to their thrones until the late twentieth century, with Sweden being the first to adopt absolute primogeniture in 1980 and other Western European monarchies following suit.

Since the adoption of absolute primogeniture by contemporary Western European monarchies, examples of female heirs apparent include Crown Princess Victoria of Sweden, Princess Catharina-Amalia of the Netherlands, and Princess Elisabeth of Belgium; they are, respectively, the oldest children of Kings Carl XVI Gustaf, Willem-Alexander, and Philippe. Princess Ingrid Alexandra of Norway is heir apparent to her father, who is heir apparent to the Norwegian throne, and Victoria herself has a female heir apparent in her oldest child, Princess Estelle. Victoria was not heir apparent from birth (in 1977), but gained the status in 1980 following a change in the Swedish Act of Succession. Her younger brother Carl Philip (born 1979) was thus heir apparent for a few months (and is a rare example of an heir apparent losing this status without a death occurring).

In 2015, pursuant to the 2011 Perth Agreement, the Commonwealth realms changed the rules of succession to the 16 thrones of Elizabeth II to absolute primogeniture, except for male heirs born before the Perth Agreement. The effects are not likely to be felt for many years; the first two heirs at the time of the agreement (Charles, Prince of Wales, and his son Prince William, Duke of Cambridge) were already eldest born children, and in 2013 William's first-born son Prince George of Cambridge became the next apparent successor.

But even in legal systems that apply male-preference primogeniture, female heirs apparent are by no means impossible: if a male heir apparent dies leaving no sons but at least one daughter, then the eldest daughter would replace her father as heir apparent to whatever throne or title is concerned, but only when it has become clear that the widow of the deceased is not pregnant. Then, as the representative of her father's line she would assume a place ahead of any more distant relatives. Such a situation has not to date occurred with the English or British throne; several times an heir apparent has died, but each example has either been childless or left a son or sons. However, there have been several female heirs apparent to British peerages (e.g. Frances Ward, 6th Baroness Dudley, and Henrietta Wentworth, 6th Baroness Wentworth).

In one special case, however, England and Scotland had a female heir apparent. The Revolution settlement that established William and Mary as joint monarchs in 1689 only gave the power to continue the succession through issue to Mary II, eldest daughter of the previous king, James II. William, by contrast, was to reign for life only, and his (hypothetical) children by a wife other than Mary would be placed in his original place (as Mary's first cousin) in the line of succession – after Mary's younger sister Anne. Thus, although after Mary's death William continued to reign, he had no power to beget direct heirs,[2] and Anne became the heir apparent for the remainder of William's reign. She eventually succeeded him as Queen of England, Scotland and Ireland.

• Parliament deposed James Francis Edward Stuart, the infant son of King James II & VII (of England and Scotland respectively) whom James II was raising as a Catholic, as the King's legal heir apparent—declaring that James had, de facto, abdicated—and offered the throne to James II's oldest daughter, the young prince's much older Protestant half-sister, Mary (along with her husband, Prince William of Orange). When the exiled King James died in 1701, his Jacobite supporters proclaimed the exiled Prince James Francis Edward as King James III of England and James VIII of Scotland; but neither he nor his descendants were ever successful in their bids for the throne.
• Crown Prince Gustav (later known as Gustav, Prince of Vasa), son of Gustav IV Adolf of Sweden, lost his place when his father was deposed and replaced by Gustav IV Adolf's aged uncle, the Duke Carl, who became Charles XIII of Sweden in 1809. The aged King Charles XIII did not have surviving sons, and Prince Gustav was the only living male of the whole dynasty (besides his deposed father), but the prince was never regarded as heir of Charles XIII, although there were factions in the Riksdag and elsewhere in Sweden who desired to preserve him, and, in the subsequent constitutional elections, supported his election as his grand-uncle's successor. Instead, the government proceeded to have a new crown prince elected (which was the proper constitutional action, if no male heir was left in the dynasty), and the Riksdag elected first August, Prince of Augustenborg, and then, after August's death, the Prince of Ponte Corvo (Marshal Jean-Baptiste Bernadotte, who acceded as Charles XIV John in 1818). The two lines united later, when Charles XIV John's great-grandson Crown Prince Gustaf (who acceded as Gustaf V in 1907) married Gustav IV Adolf's great-granddaughter Victoria of Baden, who became Crown Princess of Sweden. Thus, from Gustav VI Adolf onwards, the kings of Sweden are direct descendants of both Gustav IV Adolf and his son's replacement as crown prince, Charles XIV John.
• Prince Carl Philip of Sweden, at his birth in 1979, was heir apparent to the throne of Sweden. Less than eight months later, a change in that country's succession laws instituted absolute primogeniture, and Carl Philip was supplanted as heir apparent by his elder sister Victoria.
• Muqrin bin Abdulaziz became Crown Prince of Saudi Arabia in January 2015 upon the death of his half-brother King Abdullah bin Abdulaziz Al Saud and the accession of another half-brother, Salman bin Abdulaziz Al Saud, to the Saudi throne. In April of that year, Salman removed Muqrin as Crown Prince, replacing him with their nephew Muhammad bin Nayef. Muhammad bin Nayef himself was later replaced as Crown Prince by the king's son Mohammad bin Salman.

In some jurisdictions, an heir apparent can automatically lose that status by breaching certain constitutional rules. Today, for example:

• A British heir apparent would lose this status if he or she became a Catholic. This is the only religion-based restriction on the heir-apparent. (Previously, marrying a Catholic also equated to losing this status, however, in October 2011, the governments of the 16 Commonwealth realms —of which Queen Elizabeth II is monarch— agreed to remove the restriction on marriage to a Catholic. All of the Commonwealth realms subsequently passed legislation to implement the change, which fully took effect in March 2015.)
• Swedish Crown Princes and Crown Princesses would lose heir apparent status, according to the Act of Succession, if they married without approval of the monarch and the Government, abandoned the "pure Evangelical faith", or accepted another throne without the approval of the Riksdag.
• Dutch Princes and Princesses of Orange would lose status as heir to the throne if they married without the approval of the States-General, or simply renounced the right.
• Spanish Princes and Princesses of Asturias would lose status if they married against the express prohibition of the monarch and the Cortes.
• Belgian Dukes and Duchesses of Brabant would lose heir apparent status if they married without the consent of the monarch, or became monarch of another country.
• Danish Crown Princes and Princesses would lose status if they married without the permission of the monarch. When the monarch grants permission for a dynast to enter marriage, he may set conditions that must be met for the dynasts and/or their children to gain or maintain a place in the line of succession; this also applies for Crown Princes and Princesses.