Ancestor 100/104 John Robertson Sr

Who is John Robertson Sr?  We know that there was a Sr because clearly give his son the designation of Jr.  However, there seems to be more than one John Robertson – imagine that!  So while many family trees have named our Sr as a potential revolutionary war patriot married to Sarah Jennings, I believe that line is incorrect and so it needs a lot more research.  We have a name but that is all.