Off the top of my head, this is what I suspect. I think William Davis Barger is probably a descendant of Abraham Barger (see information here: http://freepages.genealogy.rootsweb.ancestry.com/~morrgary/families/black/tbl_black_susannah.html). The Perry, Indiana connection is pretty conclusive. Abraham Barger may prove to be a son or relative of Christian Barger (1st), the immigrant from Germany mentioned in my post on The Barger Family.
It is possible that William Davis Barger is part of this Barger family tree.He could be descended from one of Christian Barger's sons. I'll have to do some more digging. There are a couple of possibles for whom I just don't yet have their spouses' names or descendants. I'll check and get back to you.