I don't want to rely on just census records. I do know that he was dead by 1866 so he died sometime between 1836 (after his wife died) and 1866 when his son died so i don't believe he will be on any census records after at least 1861.
What a shame you didnt post this information before now; it would have saved me quite a lot of time.
If you dont give all the information that you have available, those who are trying to help you are working in the dark, wasting their time, and in the long run are restricted in the assistance they can give.
It is important to rely on census records for information and leads. From the 1841 and 1851 census information that I have posted, you now know :
Alexander was born about 1788 in Nairn
He was still alive and working as a mason in 1851
The names and approx. date of birth of 2 daughters, and the marriage information for the younger.
I strongly recommend that you search the 1861 census thoroughly for Alexander to see if you can reduce even more, the search parameters for his death.
In reply 34 I have given you the most likely birth record I could find for him, based on information from the 1851 census. It is only a possibility; and it is quite likely that there is no record of his birth.