Question: Who is Gaston, Prince Of Viana's paternal grandfather?
Sentence (from "Gaston IV, Count of Foix"): Gaston IV (27 November 1422 – 25 or 28 July 1472) was the sovereign Viscount of Béarn and the Count of Foix and Bigorre in France from 1436 to 1472.
Relevant evidence: No