The François Lacasse who married Marguerite Richard on 28 Oct 1771 was the son of Jean-Baptiste Lacasse and Marie-Josèphe Allaire (who married 1734 in Beaumont). He is thus the grandson of Joseph Casse (ou Lacasse) and Marie Bazin, and the great-grandson of Antoine Cassé and Françoise Pilois. All of the above is in Tanguay except the most recent generation, i.e. the parents of François. The information I have is based on research I personally commissioned from René Jetté. François could well have been born in Beaumont, which is where both his parents were from, but I'm not sure about the date. At his death in 14 Nov 1782, he was said to be 33 years of age. 1749 fits with that, and also with the birth dates of the other children of Jean-Baptiste Lacasse.