Well, I am not positive. It's just what has been recorded by various people. I have (at least) one 3rd cousin who has done record research, and he might know how much of this is documented and how much could be wrong, but it's pretty hard to get a reply from him.
I appreciate all you did there. I looked at deed info. on the York Archives website this morning, and I see there was also a John Gibson who sold land in Sept 1780, to Jacob Shafer.
You are quite right to question York. Maybe the answers lie in Virginia, or in KY where they went next. I'm not sure what besides a will or info. handed down through families would connect a set of children's names to their parents' names, way back then. I say "set" because just a child named James isn't much of a clue. Church records maybe, and I would guess Presbyterian, but I really don't know.
I know I looked at Jacob and Anna Whiteford Gibson recently and decided that was probably not the right line exactly.
Thank you for your generous help. I'm very sorry that it didn't lead anywhere.