Hello KurtisGale and
When you say that you hit a stumbling block at the 1881 census, I'm not sure whether you are trying to go backwards or forwards, but here's a try doing a bit of both
Is that the John B Clark age 15 in 1871, born in Kintore, working as a farm servant for James Mathieson in Fintray?
He appears to be living with his grandparents in Kintore in 1861, they are John Brown, 56 Ag lab & crofter born in "Fullgnessie" [sorry, I'm working from an Ancestry transcription] and Christina Brown, 48, born in New Machar. This might explain the middle initial 'B' in 1861 & 1871.
I don't find him in 1891, but could he be this one in 1901? The children were all born in Alford.
79 High Street, Inverurie, Aberdeenshire
John Clark, 45, Head, born Kintore, Aberdeen, Port Boy
Mary Clark, 36, Wife, born Coull, Aberdeen
James Clark, 8, Son, born Alford, Aberdeen, Scholar
Maggie Ann Clark, 3, Daur, born Alford, Aberdeen
Elizabeth Clark, 2mo, born Alford, Aberdeen
There is a marriage in Coull of a John Clark and a Mary in 1895, before the younger two children were born. This record should give John's parents.
All very well if this is, indeed, the correct John…
If you specify what you have already found and why you think the John born Kintore in 1856 is your man, maybe we can be of more help.
All the best,
Sarah