Infante Joao, was the second born son of John II of Portugal, he was born in 1482, and he died in the same year and day. However, if he had not died then and instead survived, what consequences could there have been for Portugal? He was seven years younger than his beloved older brother Afonso, so perhaps that rules him out of a marriage with Isabella of Aragon, but could he, if Afonso still dies in 1491, be married off to a sister of Isabella?
Also, with Joao perhaps being quite administratively capable, and willing to reform Portugal, with a good brain for taxes and the economy, how could this influence Portugal in the age of exploration and elsewise?