Hullo Tom,
I see that your John Wright at Lower Crannabog in 1861 age 11 and a scholar has his relationship to head of household James Jamieson recorded as being a servant. I don't see it as being particularly unusual him being a servant at age 11 but it is odd that he's also noted as a scholar. Looking at the actual census entry, I feel that him being a servant is an error in the census, the people preceding and following obviously being servants, and they being the '2 men and 1 girl' employed by the farmer James Jamieson. So, we cannot tell his real relationship from the census.
But I also see John Wright's baptism details say that he was brn 28-11-1850 bpt 21-4-1851 Marnoch natural son of John Wright "now in 12th Batn. Royal Artillery" & Isabella Simpson; registered 29 Dec 1855.
And the 1851 census shows John Wright age 4m at Castlehill in Marnoch, obviously with his mother Isabella Simpson. That Simpson family was in Castlehill for many years - Isabella herself was born there in 1827. Castlehill is east of Aberchirder towards Carnousie. The Crannabogs and Kebholes are a mile or so due north. I guess Lower Crannabog is on the OS map as Nether Crannabog.
I suspect father John Wright disappeared off the scene - do you know more on him? The National Archives at Kew should have a good deal more on John Wright's military service. Maybe there are regimental records that might identify him.
For sure, mother Isabella Simpson married George Chalmers 21 Feb 1852, and perhaps (I've seen this before) the new husband didn't welcome the presence of his stepson John Wright, this explaining why John Wright is not with his mother in 1861. Isabella Simpson & George Chalmers had five children, some of whom can be found in later years scattered around Banffshire and Aberdeenshire, but the parents seem to have evaded the censuses, in particular and annoyingly the 1861 census.
Isabel Simpson died 3 Feb 1873 age 44 in Aberchirder, a pauper albeit recorded as still married to George Chalmers a labourer - the inspector of poor was her informant. It looks as though the family had split up and she had been left to fend for herself.
So, in that context, the question is why was John Wright at Lower Crannabog in 1861? If he wasn't a servant working on the land, was he a boarder, a visitor or had he been taken in and was being brought up by Jane Geddes?
As far as I can tell, this Simpson family as a whole is unrelated to the Geddes/Jamieson family in Lower Crannabog. It's unlikely that John Wright was simply taken in by them out of the goodness of their hearts, and if he makes no reference to him being brought up in that family, then perhaps he wasn't adopted by them either. That leaves him being a (paying) temporary boarder - supporting the notion that the family was in bits.
In the course of gathering these comments, I discovered that James Geddes in Kebholes witnessed the baptism of Andrew Geddes s/o John Geddes in Brigshillock, Alvah & Mary Morison on 17 Nov 1825, and thus probably Andrew's brother James in 1822. The same James Geddes in Kebholes witnessed on 5 Mar 1834 Jane Geddes' son James in Nether Crannabog Forglen (thus the witness was the child's grandfather). That John Geddes in Brigshillock was in Slains, Abn when he married and had their first child Ann. This combination shows that Brigshillock's John and Kebholes' James are likely to be brothers, likely to have been born in Slains or thereabouts, and thus not related to 'my' James Geddes of my original post - though I need to mull that one over.
The Slains' Ann Geddes married George Simpson; they became tenants in Brigshillock and this is where one of your Chalmers was in 1881. At present, I still don't think this George Simpson is connected to your Isabella Simpson, but maybe you have more on the Simpson side.
Think that's enough to chew over! How does any of the above fit in with what you know about your Simpsons and Wrights?