Hi, I'm also researching Gendron's (Jandrew, Gendreau, etc) in Ontario. My direct ancestor was Rapheal Gendron originally from the Chateauguay Region of Quebec. Raphael, wife Sophie, and children moved to the Frankford, Hastings Co., Ontario ca. 1855. While in Ontario the spelling of their surname changed from the correct "Gendron" to Jandrew or Gendreau.
Also, during post 1850 to at least 1901 there was Fabien Jandrew, wife Catherine, and/or children, living in the Rawdon, Hastings Co., Ontario, area. I'm not sure if Rapheal and Fabien were related.
So far I haven't come across any of the names already listed on this message board but I'll keep my eyes open and post anything new I dig up. Hope I helped someone....