I saw your posting and looked up Eusebe Lafontaine. I found his baptismal record and it states the name of his parents. They match the names of the parents you have, so, hopefully, this provides the substantiating link you sought. The record information is as follows:
St Joseph’s at Cooperville, NY, baptismal record dated July 12, 1857 states, in French, (not verbatim) that Eusebe Lafontaine was born July 2 to Simon Lafontaine and Sophie Lavoie of this parish. Parrain (godfather) Eusebe Lavoie; marrain (godmother) Marguerite Languedoc/Languedoe. This is on page 26 of records for 1 June 1856 to 28 February 1864. This was viewed via Ancestry.com and is part of the Drouin Collection.