I found the marriage for George and Leontine, although he is listed in the index as George Rouge
Quebec, Vital and Church Records (Drouin Collection), 1621-1967 about Leontine Lapointe Name: Leontine Lapointe Spouse: George Rouge Event: Mariage (Marriage) Marriage Year: 1877 Marriage Location: Kamouraska, Québec (Quebec) Place of Worship or Institution: St-Louis
I expected to find them in same place as birth of first child but that is not always the case. In this case they married in the Parish where Leontine was from.
The image of the record says (will domy best with my French)
October 9, 1877 after dispensing of banns, marriage of George St. Onge, major son of Jean Marie St. Onge, cultivator and Louise Ouellet of the Parish of St. Jonquiere on the first part and of Leontine Lapointe, major daughter of Abraham Lapointe and Christine Ouellet of this Parish. In the presence of Emile St. Onge, brother of the spouse, Napoleon Lapointe, brother of the espouse, Eliza Lapointeand Victor Bouchard, friends of the spouses.
There is a marriage for a Jean Bte. St. Onge and a Marie Louise Ouellet in 1841 which may be the right couple , married in Set-Anne-de-la-Pocatiere Jean Bte. is shown as Jean Baptiste Paillant dit St. Onge
There is a family in St. Denis, Kamouraska in 1861 which would fit with this date of marriage as eldest child is age 19 - son George is age 9 so born about 1852 which seems to fit for your George. In 1871 father is shown as Jean Marie St. Onge so that fits. Family still in Kamouraska in 1861 he is J. Marie.
Let me know if you would like that info. One of the children is Louise born about 1857 and I found her baptism and it shows father as Jean Marie St. Onge so not sure about the Jean Marie/Jean Bte.?? Mother is Marie Louise Ouellet
From the census that I found - IF it is the right family, then it looks like George was a twin with twin sister Georgina.
Let me know if you would like more on this family.