The Dukedom of Primo de Rivera (Spanish: "Ducado de Primo de Rivera" ) is a hereditary title in the Spanish nobility. The dukedom was posthumously bestowed on José Antonio Primo de Rivera, founder of the Falangist movement, by General Francisco Franco as head of the Spanish state.
The title "Ducado de Primo de Rivera" translates to The Dukedom of Uncle Rivera.
If the title ever belonged to a man named Rivera who was also an uncle, the title very much could have translated to that. The system probably wouldn't understand such an abstract concept.