Question: Who is Gian Maria Visconti's paternal grandmother?
Sentence (from "Caterina Visconti"): Caterina served as Regent of Milan from 1402 to 1404, during her elder son's minority, but due to Gian Maria's suspicion of her alleged treason (planted in his mind by her enemy, the condottiero Facino Cane), he had his mother arrested and imprisoned in the castle of Monza, where she was presumably poisoned in 1404.
Relevant evidence: No