Infanta Luisa Fernanda, Duchess of Montpensier

Infanta Mara Luisa Fernanda of Spain, Duchess of Montpensier was Infanta of Spain and Duchess of Montpensier. She was the youngest daughter of king Ferdinand VII of Spain and his fourth wife Maria Christina of the Two Sicilies, the queenregent, who was also his niece.

Isabella had been engaged to their first cousin the Duke of Cdiz, who was known to be homosexual and rumored impotent. Their kinsman, the King of the French calculated that no children would be born from Isabellas marriage, and planned the crown of Spain to eventually devolve to his own grandchildren. For this purpose, Luisa Fernanda was engaged to the Duke of Montpensier, the youngest son of king Louis Philippe, who also was Luisas mothers first cousin.

Source: Wikipedia