(1) The Crown of Spain shall be inherited by the successors of H. M. Juan Carlos I de Borbón, the legitimate heir of the historic dynasty. Succession to the throne shall follow the regular order of primogeniture and representation, the first line always having preference over subsequent lines; within the same line, the closer grade over the more remote; within the same grade, the male over the female, and in the same sex, the elder over the younger.
(3) Should all the lines designated by law become extinct, the Cortes Generales shall provide for succession to the Crown in the manner most suitable to the interests of Spain.
(4) Those persons with a right of succession to the throne who marry against the express prohibition of the King and the Cortes Generales, shall be excluded from succession to the Crown, as shall their descendants.
… (Sec. 57)