Nyorai kuenderera mberi kwechikamu chino - Isabella's claims to it were not secure, since her marriage to Ferdinand enraged her half-brother Henry IV of Castile and he withdrew his support for her being his heiress presumptive that had been codified in the Treaty of the Bulls of Guisando. Henry pachinzvimbo akaziva Joanna weCastile, akaberekwa panguva yemuchato wake naJoanna wePortugal, asi baba vake vaive vasina chokwadi, sezvo Henry akanzwika kuti aive asina simba. Apo Henry akafa muna 1474, Isabella akataura kuti aida chigaro choumambo, icho chakakwikwidzwa naJoanna ane makore gumi nematatu. Joanna akatsvaka betsero yomurume wake (uyo akanga ariwo babamunini vake), Afonso V wePortugal, kuti atore chigaro. Iyi gakava pakati pevanokwikwidza vakwikwidzi yakatungamirira kuHondo ya1475<unk>1479
. Isabella akakumbira kubatsirwa naAragon, murume wake, mugari wenhaka, uye baba vake, Juan II weAragon vachimupa rubatsiro. Kunyange zvazvo Aragon yakapa rutsigiro rwechinangwa chaIsabella, vatsigiri vaIsabella vakanga vawana zvibvumirano, Isabella akabvumwa semugari wenhaka oga wekorona yeCastile. Juan II akafa muna 1479, uye Ferdinand akagara pachigaro choumambo muna January 1479.