This is what I currently have with regards to sibblings of Joseph Arpin, son of Joseph Arpin (#1) & Christine St-Michel.

1. Maglorine (Magloire, Maglorinie) Arpin, b. 1876; d. 10 April 1897 St-Robert, QC; m. 21 april 1896 St-Robert, QC Noé Robidoux, b. circa 1874, d. ? (father: Joseph Robidoux mother: Philomène Badayac dit Laplante)
2. Graziella Arpin, b. 12 July 1877; d. ?; m. 4 Feb 1896 St-Robert, QC Antoine Benoît, b. 8 March 1871; d. ? (father: Pierre (possibly Antoine)Benoit mother: Marie Proulx) - Moved to USA with his wife & children after 1911 (possibly Springfield, MA).
3. Marie Arpin, b. 21 (1 ?) Feb 1879 St-Robert, QC; d. ?, m. 11 Sept 1900 St-Robert, QC Basile O. Benoit, b. 1878 or 1877, d. ? (father: Pierre Benoit mother: Marie Proulx)
4. Joseph (#2) Arpin, b. 1 July 1881 St-Robert QC; d. 2 April 1962 (65 ?), m. 7 jan 1908 St-Malo, MB Anna Morin, b. 5 June 1886 St-Malo, MB, d. 19 Feb 1962 St-Malo, MB (father: David Morin mother: Philomène(-Joséphine) Marcotte)
5. Cordélie (Cordélia) Arpin, b. 16 May 1883 St-Robert, QC; d. 25 Feb 1977 St-Robert, QC; m. 15 Feb 1909 (1904 ?) St-Robert, QC Joseph Cournoyer, b. circa 1879, d. ? (father: Joseph Cournoyer mother: Elmire Ethier)
6. Ozina (Osina) (Marie Ozina-Rose) Arpin, b. 6 March 1885 (1891 ?) St-Robert, QC; d. 31 Oct 1921 St-Robert, QC; m. 7 Feb 1911 St-Robert, QC Félix Lavallée, b. 1 June 1886, d. ? (father: Pierre Lavallée mother: Catherine Dumas) Note: Is Ozina = Euphrosine?
7. Delphis Arpin, b. circa 1875 or 1874, d. 1939 (probably Leominster, MA - St-Cecilia’s Parrish.); m. 13 Nov 1900 Ste-Victoire-de-Sorel, QC Rose-Anna (Marie) Donais (Daunais), m. 3 Dec 1881 Ste-Victoire-de-Sorel, QC; d. ? (probably Leominster, MA - St-Cecilia’s Parrish) (father: François Donais (Daunais) mother: Vitaline Bardier) - Emmigrated with his family to Leominster, MA.
8. (J.) Rodolphe(-Félix) Arpin, b. 1 Feb 1887 St-Robert, QC; d. ? (after Dec 2005, possibly at Leominster, MA - St. Cecilia’s Church); m. 19 Feb 1917 St-Robert, QC Aurore Cournoyer, b. circa 1897 (Sept 1899 ? Canadian census of 1911 notes Aurore, daughter of widow Célanire); d. ? (father: Joachim Cournoyer mother: Marie-Célina Latraverse) - Possibly emmigrated to Boston, MA and owned a liquor store in the 1950s.
9. Philias Arpin, b. 21 oct 1889 St-Robert, QC; d. 2 Nov 1974 St-Robert, QC never married
10. (J.-Pierre) Arthur (Pierre-Arthur ?) Arpin, b. 21 Oct 1891 Ste-Victoire-de-Sorel, QC; d. 18 Aug 1899 St-Robert, QC
11. Napoléon Arpin, b. 1893 (1898 ?), d. 27 Nov 1978 St-Robert, QC; m. 13 Jan 1920 St-Aimé, Massueville, QC Mélina Giguère, b. circa 1900, d. ? (father: Sigefroi (Jean Zifroye) Giguère mother: Angèle Paulhus (Paul-Hus))
12. Zéphirin Arpin, b. 11 Dec 1896 St-Robert, QC; d. 3 Feb 1917 St-Robert, QC (Died at the age of 19 while a student at Ecole Lalime in St-Hyacinthe, QC)
13. Antoine ??? Arpin, n. ?, d. ? (possibly alternate name of one of the individuals noted above or may have died in early infancy)