Question: Who is Gaston, Prince Of Viana's paternal grandfather?
Sentence (from "Gaston, Prince of Viana"): Gaston, Prince of Viana, also called Gaston de Foix (1445 – 23 November 1470), was the son of Gaston IV of Foix and Eleanor of Navarre, and was the heir of both.
Relevant evidence: Yes