How do I know the person I found is my ancestor?

Hello all,

From what I can tell, I would be a G6 Canadian. I have a death record from my G1 ancestor (born in Rochester, NY) and several U.S. Census forms for his brother that all say their parents were born in Canada. According to a biography I found of my G1 uncle, my G0 ancestor moved to Rochester, NY in the early 1830s and married his wife (also Canadian born) in 1834.

I have found several people with the right name, born at the right time in BANQ or Généologie Québec, but how do I know if any of them are the right person ? I am not sure about location or particular parishes. Is this just family history knowledge for many people?