The libretto for Verdi's first original grand opera for Paris (Les Vespres Siciliennes) was initially about the Duke of Alva, a nobleman under Philip II of Spain. The subject was changed after Donizetti died and Scribe decided to recycle the libretto for the uncompleted work. Verdi got grief for this little bit of trickery later on.
When Verdi came to create his second original grand opera (Don Carlos), the Duke of Alva was in the source material as a character but Verdi eliminated him. Coincidence? Maybe.