I have found 4 births as follows:
John Shaw B: 10/4/1820 - Tomintoul
Alexander Shaw B: 1/11/1824 - Tomintoul *4 year gap from John
Duncan Shaw B: 15/8/1826 - Tomintoul * 2 year gap from Alexander
Elspet Shaw B: 4/12/1834 - Tomintoul * 8 year gap from Duncan
All born to a Alexander Shaw + Elspet Gordon, Tomintoul, but; I could find no others via Scotlands People to these parents . . .
Only deaths found: via Scotlands People . . .
ELSPET SHAW - aged 80 - 2/2/1834 - Tomintoul
ELSPET GORDON - aged 26 - 02/02/1835 - Forfar
A little very simple arithmetic and elementary logic will show you that neither of these can be the Elspet Gordon you are looking for.
If the older one died at age 80 on 2 February 1834, it is absolutely impossible for her to be the mother of a child born in 1834, or indeed of a child born 14 years earlier, in 1820, when she would have been 64 years old. Quite apart from the fact that Elspet Shaw, daughter of Alexander Shaw and Elspet Gordon, was not born until 10 months after her death.
As for the younger one, if she died aged 26 on 2 February 1835, she must have been born between 3 February 1808 and 2 February 1809, so she would have been at most 11 years old when John Shaw was conceived in the summer of 1819.
BTW you have missed some of the children of Alexander Shaw and Elspet Gordon: there are actually seven of them, all listed in the RC registers at Scotland's People.
Donald, baptised 2 June 1818
John, 10 April 1820
Jane, 9 April 1822
Alexander, 3 October 1824
Duncan, 21 August 1826
Unnamed, baptised 6 July 1828
Elspet, born and baptised 4 December 1834.
It would also not surprise me if there is a mistake in the registers and the two baptisms
Unnamed, 3 May 1830
James, 28 October 1832
were born to Alexander Shaw and Elspet Gordon, not John Shaw and Elspet Gordon. If I were you I would look at those two baptisms as well as at the seven others. The references to them in LIBINDX give their place of birth as Stronevaich. The marriage in 1817 might also be the same couple with the groom's name incorrectly recorded. Have you viewed all the original records of these events?
And of course the Elspet Gordon who died in Forfar in 1835 would only have been at most 9 years old when Donald Shaw was conceived in the summer of 1817.
The question here is, is the Rev. Father John Shaw and John Shaw of Stonaviach/Stronevach the same person as the late of Rev. Father John Shaw who was born also in 1820 and died on 3/11/1885, as on his death it is claimeded he was born in Perth and Kinross, Kirkmichael, given Kirkmichael covered a wide area, so do we really have the same man here
Scottish death certificates do not tell you where the deceased was born. Where did this claim come from?
Kirkmichael does not 'cover a wide area'. There are four entirely separate parishes named Kirkmichael in Scotland. One is in Banffshire, around Tomintoul, and another is in Perthshire. Are you sure that this claim did not result from someone knowing that he came from Kirkmichael who had heard of the parish of that name in Perthshire but not of the one in Banffshire, so just assumed that it was the Perthshire one?
As he died in Scotland there is no need to flap around asking questions when you can easily settle the matter by looking at his death certificate, then you will see at once if he was the son of Alexander Shaw and Elspet Gordon.
There is in fact an obituary in the Lanarkshire Upper Ward Examiner of 7 November 1885 which states specifically that he was born in Tomintoul, Banffshire, in the year 1820, and the 1881 census says he was born in the parish of Kirkmichael, Banffshire.