This is from the book "Data on Demers/Dumais Families in Quebec 1648-1835 [It is slightly different than what you had]
Paul Demers. Lived at Chambly. m. 18 Jan 1762 at St. Charles to Marie-Louise Baigne (Gaignet, Begnet, Begnets, Bequet), daughter of Louis Baigne and Marie Anne Bourbeau.
Joseph Dumets/Demers, baptized 29 Jul 1704, married 6 Feb 1731 at Boucherville, to Marie-Josephte Poirier, b. 1713 - buried 8 Mar 1722, at St. Antoine-de-Chambly (St.-Antoine-sur-Richelieu, daugher of Daniel Poirier and Catherine Viger.
Children listed for Paul Demers and Marie Louise Baigne:
Joseph Demers - lived at St.-Jean-Francois. (m1) 30 Jan 1797 at Lacadie, to Marie-Osithe Comeau, daughter of Joseph Comeau and Marguerite Vincent; m (2) 3 Jul 1815 at Lacadie, to Olive Tremblay, daughter of Michel Tremblay and Marie Anne Leclair.
Children listed under Joseph:
-Judith Demers m 13 Jan 1829 at Lacadie to Pascal Signovigny (Signori), son of David Signori and Jartine Suare, of Italy.
-Marguerite Demers m 4 Sep 1827 at Lacadi to Antoine Marchesseault, wider of Marie Auget, of Napierville.
-Marie Louise Demers m. 13 Aug 1822 at Lacadie to Isaac Piedalue, son of Joseph Piedalue and Genevieve Patenaude.
-Marie-Osithe Demers m. 28 Oct 1816 at Lacadie to Jean-Baptiste Bouchard, son of Etienne Bouchard and Marie-Anne Babeux.
-Sophie Demers m 17 Jun 1816 at Lacadie to Jean Souter.
- Febronie Dumay, b 27 May 1822, at Assumption, Sandwich, Ontario, bur. 5 Nov 1825
-Marie-Anne Dumay, b 27 May 1824, Assumption, Sandwich, Ontario
-Marie-Olive Demers, m 17 Aug 1828, Assumption, Sandwich, Ontario to Eli Robert, b 1796, bur. 10 Jul 1835, Assumption, Sandwich, son of Paul Roberge and Therese Huard.
Siblings of Paul Demers are:
Marie-Louise Dumets/Demers Marie-Genevieve Dumets Elisabeth Dumets/Demers Marie-Joseph Dumets/Demers Marie-Gertrude Dumets/Demers Joseph Demers
Line goes like this:
Paul Demers and Marie-Louise Beignet (various spellings) Joseph Demers and Marie-Josephe Poirier Robert Demers and Marie-Madeleine Jette Andre Demers and Marie Chefdeville Jean Demers and Barbe Mauger Adrien Demers and Catherine Pougnye Jehan Demers and Marguerite Berservoyse
I don't have any info on Osithe Comeau but you can find her pedigree on rootsweb.com under Osithe Comeau.