Here is what the Family Search Site has on Jonas and Parthenia. Does your book on the Congers give the names of their children? If so, could you check to see if Robert Eli is in the list? Below is a list of the children, but as you will note, the listing for 1 & 2 is only M Conger.
Jonas CONGER (AFN: 4KHZ-T5)Sex:MFamily
Event(s) Birth:Abt. 1793 Pendleton Dist., Anderson, Sc Death:29 Nov 1836 , Gwinnett Co., Ga