BTW I see that Thomas Graham, aged 63, died in the parish of Kincardine and Croick in 1855. If you have not already got this certificate, go for it. An 1855 certificate is a gold mine of information, because in 1855 details were collected that were not collected in any other year. These include parents' names, place of birth, and names and ages of any children, both living and deceased.
According to the index at SP Thomas Graham and Grizel MacLeod had
William, baptised 12 February 1827
Thomas, baptised 14 September 1829
Grizel, baptised 27 July 1831
Donald, baptised 25 May 1832
Robert, baptised 19 June 1835
Isabella, baptised 12 February 1837
Ann, baptised 13 June 1839
Catherine, baptised 12 August 1841
all in the parish of Kincardine and Croick.
However the 1851 census lists children not in the register of baptisms. Again using only the index on SP, the Graham household includes Thomas, 57; Grace, 50; Alexander, 28; Eliza, 26; William, 22; Thomas, 20; Robert, 14; Isabella, 12; Ann, 10; and Catherine, 8.
Looking for Alexander in 1841, I note with interest that in 1841 the household at Corriemore consisted of John Graham, 20, shepherd, and Alexander Graham, 17. Is this Thomas and Grizel's son? Could John be another son of Thomas and Grizel?
In 1841 the household at Corriemuillie includes all the children from Elizabeth to Ann, two possible servants and Elizabeth Graham, 80. I speculate that Elizabeth is Thomas' mother. You can look up the full transcription at
https://www.freecen.org.uk/cgi/search.pl. Note that Grizel is recorded as Grace Macleod. This is not in any way significant, because married women in Scotland do not lose their own maiden surname on marriage, and it was not unusual for them to be referred to by their own name rather than by their husband's surname.