Joćo was born in June 3 1537 in Evora and became the heir to the throne of Portugal in 1539. He survived his four older brothers that died in childhood, but was a sickly teenager. The successive inter-marriages between the houses of Spain and Portugal had probably some responsibility on his ill health. In 1552 he married Joan of Habsburg, princess of Spain and his direct cousin, through both paternal and maternal line.
Joćo died of what the sources refer to as consumption in January 2 1554. Eighteen days later, a posthumous son was born from his marriage: future king Sebastian I of Portugal. His death with only eighteen years old was the beginning of the succession problem in Portugal that would end in the loss of independence to Spain in 1580.