Isabella of Aragon, Queen of Portugal

Isabella, Princess of Asturias was a Queen consort of Portugal and heiress presumptive of King Ferdinand II of Aragon and Queen Isabella I of Castile, as their eldest daughter. Her younger sisters were Catherine, Queen of England, Queen Joanna I of Castile, and Maria, Queen of Portugal.

Isabella was the eldest child of Ferdinand II of Aragon and Isabella I of Castile. Born during the reign of her uncle, Henry IV of Castile, the early years of her life were defined by the tension between him and her mother, as her uncle would not forgive her mother for marrying Ferdinand without his permission. Upon the death of Henry IV in 1474, Isabellas mother claimed the throne of Castile, and the young Isabella was swiftly sworn as the heiress to the throne.

Source: Wikipedia