I think that we are talking about two entirely different and probably unrelated families. The 1871 census index (which is online) shows the following heads of household in Saugeen Twp, Bruce County:
John Anderson, b. Ontario, age 31 James McVittie, b. Scotland, age 60 George McVittie, b. Scotland, age 33
This looks to be your John Anderson and Mary McVeety, who had married two years earlier. The other two McVitties are probably her relatives. If I had to guess, I would say her father (or Uncle) and brother (or cousin). More could be learned by examining the actual census records for 1871 and also for 1861 and 1851. Note that this McVittie family unit came from Scotland sometime after 1838 (if the census records are to be believed).
In contrast, my McVeetys came from Ireland (not Scotland)and settled in Lanark County before 1820. In 1871, the Thomas McVeety that you thought might be your Mary McVeety's father is living in Lanark County (listed as Thomas McVetie, b. Ontario, age 50). At some point, his son James McVeety moved to Elderslie Twp in Bruce County, but the 1909 obit of my Mary McVeety suggests that she and her father were still living in Lanark County at that time. (i.e., the obit is in the Perth paper and refers to Thomas McVeety as if he lives locally.)
Sorry if I misled you with my earlier posts, but I think that your best bet now is to research the census and other records for Saugeen Twp in Bruce County. Good luck.