Thanks for pointing out the oddity. I collected most of this information before the days of the internet and at times it was a best guess who was a child of who as. The ancetry of William James McG. who married Sarah Campbell should be as follows:
John McGibbon (1767) & Mary Anderson
-- Wiliam John McGibbon (1795) & Euphemia Taylor
-- Walter McGibbon (1832-1909) & Jane McFaddin
-- William James McGibbon (1863-1945)
(m1) Lillian Stark
(m2) Sarah Campbell
The second marriage was probably what confused me.
As for the other additional child, it appears that Walter & James Walter are likely the same person -- but came from two sources and was different enough to cause me to make two entries for future reference... One of the sources was a McGibbon descendant who has since passed away and the other source was church records.