Prince Pedro, Duke of Calabria

Regardless, the Papal Brief of 1698 and Bull of 1718 established that the grand mastership was not tied to any temporal sovereignty but was a separate inheritance of the Farnese family, and so it is the mainstream academic view that succession is not linked to the throne of Naples and Sicily.

Following this logic, at the very least, the headship and grand magistry of the Constantinian Order would fall on Prince Pedro.

In due course, Prince Carlo inherited his share of properties of the royal family in Italy, despite the purported renunciation, with no objection by his brothers and sisters.

He graduated as an agricultural engineer from the University of Castilla-La Mancha, and completed his Spanish military service in the Royal Guard.

He manages the family estate, La Toledana in Ciudad Real, Spain, as well as other landed estates in Spain and Austria.

This document, known as the Act of Cannes, was signed in purported obedience to the 1759 Pragmatic Sanction signed by Charles III of Spain where it was established that the thrones of Spain and Naples should never be united in the person of the same monarch, separating them forever to preserve the European balance of power.

The newly independent Kingdom of Naples was ceded by Charles III of Spain to his third child, who would become Ferdinand I of Naples.

This would establish the kings of Naples and Sicily as cadet members of the Spanish royal family, and so the country enjoyed strong relationships with its 'mother state', following many of its legal customs.

The Act of Cannes states:

"Before Us, Don Alfonso de Borbón, Count of Caserta... Head of the Royal House and Dynasty of the Two Sicilies... His Royal Highness Prince Don Carlos, our beloved Son, appears and declares that, preparing to marry HRH Infanta María de las Mercedes, Princess of Asturias, and assuming by such marriage the nationality and quality of Spanish Prince, undertakes to renounce by this Act and solemnly renounces, for himself and for his heirs and successors, all the right and reason to the eventual succession to the Crown of the Two Sicilies and to all the assets of the Royal House that are in Italy and elsewhere, and this according to our Laws, constitutions and Family customs, in execution of the Pragmatic Sanction of King Charles III, our Augustus ancestor, of October 6, 1759, the prescriptions of which he freely and spontaneously declares to subscribe and obey.

He also declares, in particular, to renounce for himself, his heirs and successors to the assets and values existing in Italy, Vienna and Monaco (Bavaria) and destined by His Majesty King Francis II (may God have welcomed his soul), to the foundation of a majorat for the Head of the Dynasty and of the Family of the Two Sicilies and for the constitution of an endowment fund in favor of the Royal Princesses and granddaughters of our August Father King Ferdinand (may God have welcomed his soul), of marriageable age; but preserving his rights to the part of the assets that were bequeathed to him by his late uncle King Francis II, in the event that the Italian Government, which improperly retains them, makes the due restitution and the same everything that may arrive to him by other testamentary legacies."

Supporters of the other claimant to the headship of the House of Bourbon-Two Sicilies, sometimes referred to as the Castrist faction, argue that because Prince Carlos signed this agreement, he relinquished all of his rights and those of his descendants to both the headship of the family and the Sacred Military Constantinian Order of Saint George, and so the rights currently fall on Prince Carlo, Duke of Castro.

However, supporters of Pedro, also known as the legitimists, argue that the Act of Cannes was subject to a condition that never arose and it ls terms would have only applied if Prince Carlo's wife had inherited the throne of Spain, and he had become king of the Two Sicilies, which never happened and was furthermore highly unlikely at the time the document was created.

The legitimist supporters also point out several flaws in the document and its interpretation and that it was subordinate to the Pragmatic Decree and laws of the House.

Also, they argue that the Act of Cannes never mentioned the headship of the House of Bourbon-Two Sicilies nor the grand mastership of the Constantinian Order, and so this was therefore never renounced.

On 14 December 1900, Prince Carlos, next oldest brother to the childless Prince Ferdinand, head of the House of Bourbon-Two Sicilies and immediate heir of their father, claimant to the former throne of the Two Sicilies, signed a private agreement purporting to renounce the "future succession" to the former crown before his marriage to María de las Mercedes, Princess of Asturias, heiress presumptive to the throne of Spain.

The Spanish minister of Justice had stated in the Cortes (Parliament) on 18 December 1900 that no renunciation was necessary and any such renunciation would be null and void.

He is the only son of Infante Carlos, Duke of Calabria (1938–2015), and his wife, Princess Anne of Orléans.

Prince Pedro of Bourbon-Two Sicilies, Duke of Calabria, Grandee of Spain (Pedro Juan María Alejo Saturnino de Todos los Santos; born 16 October 1968), is the only son of Infante Carlos, Duke of Calabria (1938–2015), and his wife, Princess Anne of Orléans.

As primogeniture heir of the kings of the Two Sicilies he is the principal claimant to the headship of the Royal House of Bourbon-Two Sicilies, which ruled the Kingdom of the Two Sicilies before the unification of Italy.

Pedro married Sofía Landaluce y Melgarejo (born 23 November 1973 in Madrid), daughter of José Manuel Landaluce y Domínguez and his wife María de las Nieves Blanca Melgarejo y González (granddaughter of the Dukes of San Fernando de Quiroga), on 30 March 2001 at Real Club de la Puerta de Hierro in Madrid.

Pedro and Sofía have seven children:

Pedro is the senior of the two claimants to the headship of the House of Bourbon-Two Sicilies, since the death of his father on 5 October 2015.

The other claimant is Prince Carlo, Duke of Castro.

Pedro is claimant to the grand mastership of the Constantinian Order, and the grand mastership of the Order of Saint Januarius, as well as president of the Council of the four Spanish Military Orders of Santiago, Calatrava, Alcántara and Montesa, and grand commander of the Order of Alcántara.

He is also a grandee of Spain, as the son of an infante of Spain.