Ah, makes more sense now but you hadn't mentioned the 1851 census information. An online tree I saw at the start of searches gave children William & Sarah both born c1849 but no details listed.
The 1851 census record would seem to rule out William McKeever of Cam as son of John & Betty (dates were tight be just possible if that William was born at the very start of their marriage (1842).
Revised list-
John McKeever (d.1911) m.(1842) Elizabeth “Betty” Cochrane (d.1905)
1. James McKeever (1843-1930) m. Ellen Foster
2. Sarah McKeever (c1846-1848)
3. John/William John/William McKeever (Dec.1848-1881)
4. Eliza McKeever (June 1853-aft.1921)
5. Mary A. McKeever (c1859) m. Alexander Forbes
6. David McKeever (Mar.1863) m. Ellen Kelly (c1874-1914)
7. Daniel McKeever (1865 Belraugh-1911), unm.