A recent Brazilian documentary was done about Sebastianism. For years after his death pretenders showed up claiming to be this lost King (even though remains were buried in Portugal). He was the son of John Manuel, Prince of Portugal, and his wife, Joan of Austria. After his death, many of his subjects believed that he would return to deliver them from Spanish rule, a messianic faith known as Sebastianism (Sebastianismo). He grew up and became a half-way decent king. He succeeded to the throne at the age of three, on the death of King John III, his paternal grandfather. A cult grew around this King and was still active in Brazil as late as the early 1800s. He was the son of … Sebastian was born heir-apparent to the throne of Portugal, since his birth occurred two weeks after the death of his father. Sebastian, king of Portugal from 1557, a fanatically religious ruler who lost his life in a crusade against the Muslims in Morocco. 20 January 1554; d. 4 August 1578), king of Portugal. Sebastian of Portugal Sebastian I (Sebastião I Portuguese pronunciation: [sɨbɐʃˈti.ɐ̃w̃]; 20 January 1554 - 4 August 1578) was King of Portugal and the Algarves from 11 June 1557 to 4 August 1578 and the penultimate Portuguese monarch of the House of Aviz. Sebastian of Portugal was born on 20 January 1554, the feast of Saint Sebastian, the only child and heir of John Manuel, Prince of Portugal, and his wife, Joanna of Austria. Sebastian of Portugal Sebastian "the Desired" (Sebastião I, Portuguese pronunciation: [sɨbɐʃˈti.ɐ̃w̃], o Desejado; Lisbon, 20 January 1554 – presumed to have died at Alcácer-Quibir, 4 August 1578) was the 16th king of Portugal and the Algarves. Sebastian (Sebastião) of Portugal (1554–1578) Sebastian (Sebastião) of Portugal (b.