When Lewis Bylow remarried in Michigan after the death of his wife Hannah King, he listed his parents as Francis Bylow and Catherine Lefevre.
On the 1851 census of Oneida, in addition to Lewis and Hanna Bylow (with her father Isaac King) there are
Home / 1852 / Canada West / Haldimand (county) / 111 Oneida township part 2 / p. 4d, 5a, (58)
33 Bylow (French Canadian), Stephen Labourer Upper Canada F. Wesleyan Methodist 31 M
34 Bylow (French Canadian), Jane Upper Canada F. Wesleyan Methodist 18 F
35 Bylow (French Canadian), Michal Upper Canada F. Wesleyan Methodist 1 M
36 Bylow (French Canadian), Michal Farmer Upper Canada F. Baptist 34 M
37 Bylow (French Canadian), Susanah Upper Canada F. Baptist 29 F
38 Bylow, Cathren Lower Canada Catholic 67 F
I think that Catherine born Lower Canada, aged 67 is the mother of Lewis and Julia Ann.
As to Francis Bylow, during the war of 1812
There was a Francis Boileau, Private in the Rifle Company of the 1st York Militia (Recruited by Captain Peter Robinson from the northern part of York County, it included a large number of fur traders from as far as Michilimakinac. They fought alongside native troops. Source: Soldiers of the King, Militia in War of 1812.
It's a great book with many militia list from all over Upper Canada.
Anyway, it is possible that it is the same Francis. so even though, Francis and Catherine were probably born in Lower Canada (per their children's 1891 census) they might have married in Upper Canada (which is probably why I can't find them in Drouin)
By the way, not related to the family, but very interested in the King.