While Mary's grandparents, Ferdinand and Isabella, had retained sovereignty of their own realms during their marriage, there was no precedent to follow in England.

Afonso's attempts to take over the throne of Castile were not successful after he lost a short war with Isabella of Castile and Ferdinand of Aragon.

Isabella of France, sister of Charles IV, claimed the throne for her son, Edward III of England.

At an early age, Catherine was considered a suitable wife for Arthur, Prince of Wales, the eldest son of Henry VII of England and heir to the throne, due to the English ancestry she inherited from her mother Queen Isabella I of Castile.

After the fall of the Byzantine Empire, the legitimate heir to the throne, Andreas Palaiologos, willed away his claim to Ferdinand and Isabella in 1503.

In 1868, the Spanish queen Isabella II was expelled by a revolution, leaving that country's throne vacant.

Contenders for the throne of Castile were Henry's one-time heir Joanna La Beltraneja, supported by Portugal and France, and Henry's half-sister Queen Isabella I of Castile, supported by the Kingdom of Aragon and by the Castilian nobility.

The supporters of reform and of limitations on the absolutist rule of the Spanish throne rallied behind Isabella and the regent, Maria Christina ; these reformists were called " Cristinos.

The next year, Isabella died giving birth to their son Conrad IV, who succeeded his mother to the throne although he never appeared in the east.

This was disputed by another branch of the Lusignan family: Maria of Antioch, daughter of Bohemond IV of Antioch and Melisende of Lusignan ( herself a daughter of Isabella I and Amalric II ), claimed the throne as the oldest living relative of Isabella I, but for the moment her claim was ignored.

* January 20 – Ferdinand II ascends the throne of Aragon and rules together with his wife Isabella I, Queen of Castile over most of the Iberian peninsula.

The conflict was a culmination of years of tension between the two nations, which finally came to a head over the issue of a Hohenzollern candidate for the vacant Spanish throne, following the deposition of Isabella II in 1868.

Despite his many marriages he did not have a son so on 30 June 1833 he was influenced by his wife to abolish the Salic Law so that her daughter, Isabella, could become queen depriving his brother, Don Carlos, of the throne.

# The Quadruple Alliance of April 1834 was formed by the United Kingdom, France, Spain, and Portugal to support queen Isabella II of Spain against her uncle Don Carlos, Count of Molina, who claimed the Spanish throne under the succession law of 1714-1830, and queen Maria II of Portugal ( represented by her father Pedro, 18th Duke of Braganza, former Emperor of Brazil and King of Portugal ) against her uncle Miguel of Portugal, who proclaimed himself absolute king before the Portuguese Liberal War.

Edward's claim on the French throne was based on his descent from King Philip IV of France, through his mother Isabella.

In a move guaranteed to appeal to domestic opinion, Isabella also decided to pursue Edward III's claim on the French throne, sending her advisers to France to demand official recognition of his claim.

In Derek Jarman's 1991 film based on Marlowe's play, Isabella is played by actress Tilda Swinton as a ' femme fatale ' whose thwarted love for Edward causes her to turn against him and steal his throne.

Philippa married Edward at York Minster, on 24 January 1328, eleven months after his accession to the English throne ; although, the de facto rulers of the kingdom were his mother, Queen Dowager Isabella and her avaricious lover Roger Mortimer, 1st Earl of March, who jointly acted as his regents.

Hence, Clarence participated in Warwick's schemes, marrying the earl's daughter Isabella, believing he could gain his brother's throne.

In England, Isabella of France heard the news and claimed the throne on behalf of her son.

Due to Philip II being a grandson of Manuel I of Portugal through his mother Isabella, Philip was in the line of succession to the throne of Portugal, and claimed it after Sebastian of Portugal was killed in the Battle of Alcácer Quibir in 1578, thus establishing the Iberian Union.

Pursuant to the terms of the Treaty of Paris ( 1303 ), the marriage of Philip's daughter Isabella to the Prince of Wales, heir of Philip's enemy, celebrated at Boulogne, 25 January 1308, was meant to seal a peace ; instead it would produce an eventual English claimant to the French throne itself, and the Hundred Years War.

Philip was one of the two chief claimants to the throne along with the demands of Dowager Queen Isabella of England, the late King Charles ' sister, who claimed the French throne for her young son King Edward III of England.

* 1327 – Teenaged Edward III is crowned King of England, but the country is ruled by his mother Queen Isabella and her lover Roger Mortimer.

After the death of her husband, Isabella ruled Mantua as regent for her son, Federico.

This was not enough to satisfy Isabella, already in her mid-60s, so she returned to political life and ruled Solarolo, in Romagna until her death on 13 February 1539.

Isabella was born into a royal family that ruled the most powerful state in Western Europe.

Isabella ruled as regent until 1330, when Isabella's son, Edward deposed Mortimer in turn and ruling directly in his own right.

Isabella and Mortimer ruled together for four years, with Isabella's period as regent marked by the acquisition of huge sums of money and land.

In 1503, Queen Isabella ruled that only people who were better off under slavery ( a definition which explicitly included cannibals ) could legally be taken as slaves.

The Royal Pantheon contains the tombs of the Holy Roman Emperor, Charles V ( who ruled Spain as King Charles I ), Philip II, Philip III, Philip IV, Charles II, Louis I, Charles III, Charles IV, Ferdinand VII, Isabella II, Alfonso XII, and Alfonso XIII.

As the king was young Mortimer and Isabella ruled in his name.

Emperor Frederick II, the heir to the crown of Jerusalem and Isabella of Brienne ( 9 November 1225 ) started from the port of Brindisi in 1227 for the Sixth Crusade Like other Pugliese ports, Brindisi for a short while was ruled by Venice, but was soon reconquered by Spain.

* Isabella of Armenia ( died c. 1252 ), ruled the Armenian Kingdom of Cilicia from 1219 to 1252, married to Hetoum I

Though the latter was crowned as Edward III of England on 25 January 1327, the country was ruled by Mortimer and Isabella, who were widely believed to have arranged the murder of Edward II the following September at Berkeley Castle.

Beginning in 1601, the couple ruled the Spanish Netherlands together, and after Albert's death Isabella was appointed Governor of the Netherlands on behalf of the King of Spain.

Isabella inherited the duchy from her father upon his death, and ruled jointly with her husband, Duke René of Anjou, also Duke of Bar and King of Naples, whom she had married in 1419.

After Isabella died, Philip ( who ruled Oultrejordain 1161 – 1168 ) became a warrior-monk and finally Grand Master of the Knights Templar.

The Queen of Spain was accepted by both parties, and in 1865 Isabella II ruled on the issue, deciding in favor of the Venezuelans.

* 1479 20 January – Queen Isabella I of Castile and King Ferdinand II of Aragon – the Catholic Monarchs, jointly rule the kingdoms of Castile and Aragon, including Gibraltar.

Archduke Albert VII of Austria ( 13 November 1559 – 13 July 1621 ) was, jointly with his wife, the Infanta Isabella Clara Eugenia, sovereign of the Habsburg Netherlands between 1598 and 1621, ruling the Habsburg territories in the southern Low Countries and the north of modern France.