Infante don Alfonso de Trastamare y Aviz, Prince of Asturias (1453-68) was the figurehead of rebelling magnates against his brother Henry IV of Castile. HRH The Prince of Asturias The title Prince of Asturias is given to the heir apparent to the Spanish throne, and the earlier kingdom of León. ... Henry IV of Castile, nicknamed the Impotent (ruled 1454-1474), was not a strong king. ...

Alfonso was born as the only surviving son of Isabel de Portugal, queen, and her husband John II of Castile, whose second marriage that was. Alfonso's full sister was the future Queen Isabella I of Castile. Juan II (March 6, 1405 – July 20, 1454) was King of Castile from 1406 to 1454. ... Isabella of Castile (Spanish: Ysabel, Isabel or Isabela) (22 April 1451 - 26 November 1504) was queen of Castile. ...

In early 1460's, lords of the realm were totally dissatisfied with the ineffectual king Henry IV, and further believed that the daughter (Joanna, Princess of Asturias, aka Juana la Beltraneja) whomHenry's wife had given birth to, was not sired by Henry. The cortes forced in 1464 Henry to repudiate Joanna's paternity and to recognize Alfonso as the next king, whereby he he became Prince of Asturias in place of Joanna.

Then Alfons was used as figurehead in the further rebellions of several magnates.

However, quite young, Alfonso died of a sickness, probably plague. His sister Isabella was requested to take her brother's place as figurehead of the rebels but she declined - she conciliated with Henry and was recognized as the next monarch, which she became when Henry himself died in 1474.