Diogo's father, uncle of King John II, was believed to be the richest man in Portugal, having accumulated two duchies and numerous lordships.

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.

[2][4][5] 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.

[6][7] In 1484, Diogo was accused of being the center of a conspiracy against the crown and was stabbed to death by the king himself.

Afonso's daughter and heir, Beatrice of Lara, married the 3rd Marquis of Vila Real.