Henry IV of Castile sibling Isabella I of Castile
Joan of Portugal
The remoteness of Aragon led to an approach to Portugal. In March 1453, before his divorce from Blanche was finalised, there was no record of negotiations for the new marriage between Henry and Joan of Portugal, sister of the king Afonso V of Portugal. The first marital approaches were made in December of that year, although the negotiations were long and the proposal wasn't definitively agreed until February 1455.: 59  According to chroniclers of the time, Joan did not provide a dowry and would not have to return anything even if the marriage turned out to be a failure. The length of the negotiations and the concessions could be interpreted as caused by the concerns about the rumours of Henry's impotence.: 65–67  The wedding was celebrated in May 1455, but without an affidavit of official bull authorizing the wedding between them, although they were first cousins (their mothers were sisters) and half second cousins (their paternal grandmothers were half-sisters). On 28 February 1462, the queen gave birth to a daughter Joanna la Beltraneja, whose paternity came into question during the conflict for succession to the Castillian throne when Henry died.
Henry IV was twenty-six years old when his half-sister Isabella was born. She was the daughter of his father's second marriage in 1447, to Isabella of Portugal. Henry made a number of attempts throughout his reign to arrange a politically advantageous marriage for his much younger sister. The first attempt was when the six-year-old Isabella was betrothed to Ferdinand, son of John II of Navarre (a cadet branch of the House of Trastámara).: 35  This arrangement, however, did not last long.Death
However, in 1468, at the age of only 14, Alfonso died, most likely from the plague (although poison and slit throat have been suggested). His will left his crown to his sister, Isabella, who was asked to take her brother's place as the champion of the rebels. Shortly thereafter at the negotiation of Toros de Guisando, in which she and her allies received most of what they desired, Henry agreed to exclude Joanna la Beltraneja from the succession, and to recognize Isabella as his official heir. Though Henry continued to resist this decision when possible, his actions were ineffective, and he remained at peace with Isabella for the rest of his reign. Isabella became Castile's next monarch when he died in 1474.
After the death of the king, war broke out in Castile. Joanna was supported by Portugal, while the eventual winner, Henry's half-sister Isabella I of Castile, had the support of Aragon. France initially supported Joanna, yet in 1476, after losing the Battle of Toro, France refused to help Joanna further and in 1478 signed a peace treaty with Isabella.
brother or sister kin