Longdo @ Georgina , Udora , Can. & U.S.A

I'm searching for more information on a Francis Longdo residing in Georgina township, Udora, Canada at the time of the 1871 census. Francis was approx. 75 years old at this time with sons? Francis, age 54 and born U.S.A, and Stephen age 48 and born U.S.A. I also have a Mary, but I think she was married to one of the two sons and her age is 42. All are listed as French, Roman Catholic and the older Francis came from Quebec.
They settled in Udora, Ontario and a Margaret Longdo (one of their children) was my Great-Grandmother, married to John Watson.
We also suspect a Native Peoples lineage connected to this name...can anyone out there help me with some more insight to this somewhat rare name?
Yours,
Barb Walton