I've been admiring the way you worked out this puzzle, Mike and Monica. Fascinating stuff!
There's a Mary b 1834 to Neill MCBRIDE & Effie MCTAVISH. She's possibly/probably the Mary aged 16 in the 1851 and 24 in the 1861. But is Effie the same as Barbara or might she be an earlier wife?
There's a likely 1841 household but with a few discrepancies:
SCT1841/533/6/6/1
Clachbreck, South Knapdale
All BRODIE - all b Argyllshire
John 45 Ag Lab
Niel 40 Ag Lab
Catherine 80
Mary 30
Mary 6
Jean 4
Dugald 1
Discrepancies:
John 45 (if it's the same John) is listed as 65 in the 1851?
Is Mary, 30, the same as Barbara? Compare age (rounded down) with Barbara's 46 in 1851, 52 in 1861, and 77 at death in 1887. Or was Barbara elsewhere on census night?
Summing up the births:
All South Knapdale. Ages in 1841, 1851 and 1861 appended.
Neill MCBRIDE/Effie MCTAVISH
Mary b Oct 1834, bap 9 Feb 1835 6, 16, 24
Niel BRODY/Barbara MACTAVISH
Jean b 17 Apr, bap 1 May 1837 4, 14, -
Neill BRODIE/Barbara MCTAVISH
Dougald b 18 Aug, bap 22 Aug 1839 1, 10, -
Niel MCBRYDE/Barbara THOMSON
John b 12 Jan, bap 18 Jan 1842 -
Niel BRODDIE/Barbara MCTAVISH
Catherine b 1 Mar, bap 30 Mar 1843 -, 7, 17
Niel BRODIE/Barbara THOMSON
John b 2 Dec 1845, bap 18 Apr 1846 -, 5, 14
?
Lilias b ca Feb 1851 1m, -, -
Sharon, perhaps looking at the actual OPR entries for the births/baptisms might help? Either through ScotlandsPeople or (cheaper!) ordering in the relevant film to your local LDS Family History Centre.
JAP