Hello Averil,
I think you have Corkill overload!!
- Look at your marriage date for Robert/Cath Kissage compared to the bapts.
The children you have listed were those of John Corkill & Ann Kissag, and included the brothers Robert 1770-1807 [will] who married Catharine Kissage/Kissack 1794, and William 1781-1833. William was his youngest brother and I think married Elinor Christian [both in brother Robert's 1808 will docs].
James Corkill who married Bahee Lawson d.1815 [will] was one of the four sons of James 1707-1779 [will] & second wife Cath, and brother of John who married Ann Kissag.
This is the James who CR said had lots of descendants. Unfortunately most of them were ostensibly through his son William b.1779 and have been put on those Ancestry trees, but I think she had the wrong William (previous messages). An easy mistake to make when there were so many same names/same dates, and she was looking at dozens of families, not just Corkill.
Sue