This new semi-Salic, succession law of the defunct Kingdom of the Two Sicilies was laid out by Charles III in the Pragmatic Decree of 6 October 1759, and established a secondogeniture similar to that governing the successions to Tuscany and Modena in the House of Austria. The treaties of Vienna and Naples required that King Charles separate the Spanish crown from the Italian sovereignties by designating Don Charles, his second surviving son (the eldest being severely mentally handicapped), as Prince of Asturias, the heir apparent to Spain, while his 'Italian sovereignty' would pass immediately to his third son and his descendants in the male line, Infante Don Ferdinand, and then, in the event of the death of the latter without male heirs, to Charles's younger sons and their descendants, by primogeniture.
