As you probably know, a back door could be to prove that George was a brother of a proved son of John's. The estate records listed a few unappraised items in John's estate, including a family bible. "Next of kin", John C Mohler, bought everything. Who knows, maybe it's still floating around out there,
Have you contacted the Morgan county genealogical society? They helped me greatly 20+ years ago.
I'm still trying to figure out how my Elizabeth Moler (m Joseph Pettet) fits in to this family. I suspect she was a granddaughter of Casper's but I can't make her fit anywhere.