 Gradually, the couple gained a larger number of supporters and obtained a papal bull sanctioning their marriage from Pope Sixtus IV in 1472 and gained the support of the powerful Mendoza family in 1473.When Henry IV died in December 1474, both candidates for the throne were proclaimed Queen of Castile by their respective supporters.Aware of their position of weakness against Isabella's supporters, Joanna's supporters proposed for the 43-year-old King Afonso V of Portugal, a widower for some 20 years, to marry Joanna, his niece, and assume the throne of Castile with her.