I cannot produce proof of what I am writing here but by presumption, I think parents of Benjamin Bégin are Benjamin Bégin and Ursule Talbot (m. July 17,1849 S. Bernard). And if it's so, his grandparents are Benjamin Bégin and Angèle Noel (m. Oct 10,1823 S. Henri). Why I assume that? Because one of Adele Roy's brothers is Cyrille Roy married to Marie Bégin (August 31, 1875 Lambton) and parents of Marie Bégin are Benjamin Bégin and Ursule Talbot.
If you retreive a proof of that, I would be very interested. I will add it in our "Dictionnaire des Bégin".