Fayette County, PA was full of Revolutionary Patriots. A lot of them moved to Ohio about 1810. John is a common name in the Alexander lines, so it very possible he could be a son of someone other than Oliver. I give you credit for not settling for the closest match. I'm that way also. I have had to correct a few people who want to claim my ancestor. If you want to email me directly I will help you dig. On my Alexander side I descend from a line from Cecil County, MD. But, on my other side I have several lines from Fayette County, PA. prior to 1810. I used to know that area like the back of my hand.