So far I have managed to trace the Sauvé side of P.E.T.'s ancestry via Sarah's father Seraphin-François Sauvé who married Agnes Clark in 1849 back to the original immigrant to New France, the patriarch of all the Sauvé family in Canada. Now I want to trace the Clark line further.
Have you access to the registers of St-Polycarpe, Soulanges (or a répertoire de mariages)? That should list her parents as well as his (François Sauvé and Eugenie Lalonde).