 In that year King John III granted him the title of Duke of Aveiro.After his return from Madrid, in 1537 (where he was sent by King John III to present formal condolences to Charles V, when his wife, Empress Isabel of Portugal, died) John of Lencastre, 1st Duke of Aveiro, decided to marry to "Dona" Juliana de Lara, daughter of the 3rd Marquis of Vila Real.In 1552, he was again chosen by the King to escort, from the border to Lisbon, the Infanta Joan of Spain, who would marry John, Crown Prince of Portugal (John III only surviving son).