Given the King's advanced age and failing health, his brother Don Carlos, Fernando's father, was his heir presumptive and presumed successor.

A clique of conservative and ultramontane supporters opposed to the King's liberalism surrounded Don Carlos at the royal court in Madrid, consolidating in opposition when the King took a fourth bride, his and Carlos's niece Maria Cristina of the Two Sicilies, by whom he fathered two daughters, the future Isabella II of Spain and Infanta Luisa Fernanda.

When the king died, Don Carlos and his entourage opposed the accession to the throne of his infant niece, Isabella, whose mother nonetheless managed to obtain control as queen regent on behalf of her daughter.

Later, in June 1834 Don Carlos moved with his family to England, where they lived at Gloucester Lodge, Old Brompton Road, and later at Alverstoke Old Rectory, Hampshire.

Her sons were left in the care of their father and her older sister Maria Teresa, Princess of Beira, who eventually married Don Carlos in 1838 while staying briefly with the family in Spain during the First Carlist War.