Diogo's father, uncle of
King John II, was believed to be the richest man in Portugal, having accumulated two duchies and numerous lordships. In 1472, when his older brother
John, Duke of Viseu, died without issue, Diogo inherited his titles and estates as
Duke of Viseu and
Duke of Beja. Diogo was a popular personality at the court of his cousin King
John II, and together with
Duke Fernando II of Braganza, he was the main target of King John's centralization policies. John II sought to limit the power of the upper nobility, which had increased greatly during the reign of John's father
Afonso V of Portugal. Duke Fernando II of Braganza, husband of
Isabella of Viseu, the sister-in-law of King John II of Portugal and Diogo's sister, was the first victim of John's efforts against the Portuguese nobility. In 1483, he was imprisoned, tried and executed in
Évora. In 1484, Diogo was accused of being the center of a conspiracy against the crown and was stabbed to death by the king himself. After the execution, King John II called the duke's younger brother,
Infante Manuel of Viseu, and showed him his brother's body. He promised Manuel that he would consider him his own son. At that moment, Manuel inherited his brother Diogo's titles and estates. Duke Diogo never married, but when he was quite young he visited the
Crown of Castile, where he had a love affair with
Doña Leonor de Sotomaior y Portugal (great-granddaughter of King
Pedro I of Portugal). With her he had a natural son, Afonso de Portugal. King Manuel I of Portugal granted this nephew, Afonso de Portugal, the position of 8th
Constable of Portugal. Afonso's daughter and heir, Beatrice of Lara, married the 3rd
Marquis of Vila Real. ==See also==