Wiley G. Marchman was my GG-GF. The information that I have is that his parents were Ebenezer MARCHMAN and Mary Elizabeth DOUGLASS. I cannot remember where I got the information that they were his parents, but I believe that it may have been from the files of a Watt P. MARCHMAN who left his files to the Genealogy Room at the Washington Memorial Library in Macon, GA. I do not have the names of any siblings form Wiley G., but my information does show that his paternal grandparents were Charles MARCHMAN and Tabitha BARNES. I show six children for Charles and Tabitha: Ebenezer, Stehpen, John, James, William Riley and Nancy. I don't see a John MARCHMAN married to an Elizabeth BARNES. The John who was the son of Charles and Tabitha married Eliza McColough.
Hope this helps. Let me know if you have any questions. I will be happy to share whatever information I have that may help you.