In 1894, Carlos's father Alfonso became the head of the House of Bourbon-Two Sicilies. On marrying his first wife, Carlos renounced on 14 December 1900 his future rights of succession to the non-existent Crown of Two Sicilies in an official document, known as the Act of Cannes, subject to a requirement in the Treaty of Naples of 1759 and the Pragmatic Decree of 6 October 1759 that the Crown of Spain should not be combined with the "Italian Sovereignty".[4] In 1960, Carlos' elder brother Ferdinand died without male issue, and a dispute arose between Carlos' son Alfonso and Carlos' younger brother Ranieri on the headship of the house, this with competing claims: by the law of primogeniture, Carlos' son Alfonso was considered the heir, but Ranieri claimed that Carlos had renounced his rights and those of his descendants according to the Act of Cannes. Alfonso refuted that claim by stating that it was only a promise from his father to relinquish this right if the crown of the Kingdom of the Two Sicilies were to be united with the Spanish Crown. Since this did not happen, the act had no effect and Carlos' son Alfonso reclaimed his rights. The dispute is still not resolved. Alfonso's claim was recognised by the heads of the different lines of the House of Bourbon, although not by the head of the Orleans family,[5] and in 1983 the Spanish Council of State, following an investigation by the Ministries of Justice and Foreign Affairs, the Royal Academy of Jurisprudence and Legislation and the Institute Salazar y Castro concluded unanimously in favour of Infante Don Alfonso's only son, Prince and Infante Don Carlos, a position shared by the Spanish Royal House.[6]
^Escalafón general del Real Estamento Militar del Principado de Gerona. Girona. 2014. p. 137.{{cite book}}: CS1 maint: location missing publisher (link)
The generations indicate descent from Carlos I, under whom the crowns of Castile and Aragon were united, forming the Kingdom of Spain. Previously, the title Infante had been largely used in the different realms.