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 Canness. 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, Carlos' son Alfonso reclaimed his rights. The dispute is still not resolved. Whereas the claim of Ranieri and his descendants was supported by most royal houses in Europe,[5] the claim of Alfonso and his descendants is supported by the Spanish Royal House.[6] Also, five of the highest organs of the Spanish State, including the Council of State, investigated the dispute and concluded unanimously in favour of the line descended from Infante Don Alfonso.
^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.