Well, britt, if you need a little help, here I am...
First questions to answer...
1.-Elder brother of Luis Alfonso: Francisco died as a result of a car crash. The father, duke of Cadiz, was severely injured in the same accident. It was a deep shock for little Louis Alfonso, and things go from bad to worse: just a few months later, he saw how very young Mathilda, one of the daughters of Jean Marie Rossi, at this time husband of Carmen, was died in a boating accident.
2.-About the famous wedding between Carmen and Alfonso duke of Cadiz, I must explain carefully. He was (maybe you know it...) the elder of two sons borne by Emannuella Dampierre, an italian noblewoman, to infante don Jaime. Before his marriage with Emmanuelle, Jaime, deaf-mute, had signed a renounce to his rights to the spanish throne for him and his descendants; he was merely an infant, not the heir of the crown, when his father agreed to a marriage with Emmanuella, who has not royal blood in her veins (her father was a nobleman, without royal ancestors, and her mother was daughter of an italian prince but also of an american heiress). King Alfonso and queen Ena had no doubts about their grandsons Alfonso and Gonzalo: they were not in the line of succesion to the throne. To add more, Jaime and Emmanuella were divorced, she established herself with her lover -a rich bussinessman, I believe...- and he started a scandalous relationship with Carlotta Tiedemann. Young Alfonso and young Gonzalo had not a happy childhood, but her paternal grandmother, Ena, always tried to support them in all the ways.
Jaime was the one who gave his elder son the tittle of Duke of Bourbon. As duke of Bourbon, Alfonso settled in Spain and began a diplomatic career under Franco´s regime. He was, if I´ m not confused, appointed ambassador of Spain to Sweden. A good position, certainly. People began to spread rumours about Franco trying to choose the future king: maybe Juan Carlos of Borbon, son of don Juan and doña María de las Mercedes; maybe Alfonso duke of Bourbon, son of don Jaime with his first wife Emmanuelle or maybe Carlos-Hugo de Borbon-Parma. Carlos-Hugo, by the way, gained some points when was -romantically- married to Irene princess of Holanda: the love story made him more popular. But the great wedding was yet to come: Alfonso began to courtship María del Carmen, older granddaughter, and also favourite granddaughter, of general Franco and his wife Carmen Polo. She was a beautiful girl, with a few sad romances in her background; as she said later, she felt delighted with the idea of a true prince flying around her, but also under certain pressure that came from her family: her grandmother Carmen Polo, her mother Carmen Franco and her father, Villaverde, were more than happy. When the engagedment was announced, all the common people was sure "la Señora" -Carmen Polo- was playing, with the help of Villaverde, the game to ensure her favourite granddaughter would became queen of Spain. Franco gave to Alfonso the tittle of Duke of Cadiz with treatment of His Royal Highness; Carmen Polo was very proud using the tittle Her Royal Highness every time she adressed to her granddaughter.
PD:Sorry for the mistakes...