From the birth of Charles in Madrid on 20 January 1716, the Spanish foreign policy would try and obtain – through a series of operations started with the solemn entrance of Spain in the Quadruple Alliance through the Hague Treaty of 17 February 1720 – the recognition of Charles’ rights to the double succession of Farnese and Medici. After the Congresses and Treaties of Cambrai (1721), Vienna (1725) and Seville (1729), the Empire would accept this situation with the second Treaty of Vienna in 1731: Charles was therefore heir to the Duchies of Parma and Piacenza under the regency of his grandmother, the widow Duchess of Parma, and at the same time in Florence he was proclaimed the heir to the last Grand Duke of Tuscany who become co-tutor of the young prince.

In this way, Elisabeth Farnese achieved her first goal, but the King of Spain or his successors could not claim any right to the Italian States or be tutors of their heirs. Here we see the first root, the real motive of the existence of the two Families: Bourbon Two Sicilies and Bourbon Parma.

Under the first "family pact" of 1734, which caused the Spanish intervention in the War of Polish Succession, Charles reconquered Naples and Sicily after the decisive battle of Bitonto on 25 May 1734 and was recognised as King of Naples and Sicily by the Treaties of Vienna of 1735; in exchange he had to renounce the Duchies of Parma, Piacenza and Tuscany which would go (without Tuscany but with Guastalla) to his younger brother Philip, Head of the Royal House of the Bourbon-Parma, second-born of Elisabeth Farnese and son-in-law of Louis XV.

On 18 October 1748, when Spain was ruled by Ferdinand VI, son of Philip V, who had no heir, the Treaty of Aachen – by a special clause - ruled the succession of King Charles to the Spanish Throne. This was the situation when, on 10 August 1759, Ferdinand VI died without direct heirs.

Charles, King of Naples and Sicily, was then called to the Spanish Throne; however, due to a fundamental law of the Bourbon-Spain Family known as “New Regulation for the Succession of these Kingdoms” , followed just three days later by his Proclamation of 6 October 1759, Charles, once become King of Spain, renounced the Throne of Naples in favour of his son Ferdinand and the division of the two Royal Families was set up forever.

In particular, King Charles stated that «the line of Succession I have established will never lead to the unification of the Kingdom of Spain and the Italian Dominions, so that either the sons or the daughters of my lineage mentioned above can claim rights to the Italian States only if they are not already declared Kings of Spain or Princes of Asturias or to be declared as such».

Charles of Bourbon

So the descendants of Hildebrand (and of Charlemagne and S. Louis IX) now ruled over four thrones: France and Navarre, Spain (and its dominions), Naples and Sicily, and the Duchies of Parma and Piacenza. Four Families, from a single branch, of which no one could claim rights on the dominions of the other three, but united by blood ties and by the "family pact" that makes them allied against all external and internal enemies. In the following pages, we will analyse the history, protagonists, events and reforms of the Bourbon lineage of the Two Sicilies.