Noted your Briggs connection to Brown Co. IL; my Ggg grandfather, Elias Briggs, was b.c. 1798 and d. in Schuyler Co. IL in 1856.I believe that he was some sort of cousin to the Brown Co. Briggses, but have been unable to get an absolute lock on that.
My Elias is supposed to have been the son of a James Briggs,and this James was b.c. 1764-77 in Rowan Co. NC.Some source indicate that there was a James Briggs who was a brother to your John Lemuel Briggs)1787-1877/8, and I have a theory that this is where we tie in(but it is only a theory).
As it turns out, my grandfather was Lemuel Elias Briggs; my maternal Briggs line left Schuyler Co. IL c. 1854-5 when my Gg grandfather, also named Elias(1839-1926)moved to the Texas Frontier, settling in Coleman Co.
If you happen to have anything on James Briggs, bro. to John Lemuel Briggs, I would like a chance to discuss it with you. Regards, Larry D.H. Coats