It would be useful for people to try and help you on here to know what you have already tried, and also what information you already have.
For instance, what were the names, dates and places of his children's baptisms? Scottish families very often followed a Scottish Naming tradition pattern with their children. The first son was invariably named after the father's father; the first daughter after the mother's mother, and so on.
Their names may give also give clues to other members of John's family.
Where were all the children baptised? Does it give any more information in the register as to where John's residence might have been? Does it give any indication of the father's occupation? - always very helpful in trying to track anybody down.
What about his marriage? Does it give anymore information other than the names of the bride and groom? Ages? Residence? Occupation?
Have you looked for John in any of the Censuses? Marrying in 1791, born let's say 1770 - he could just have lived until 1841. What about his children? Have you found them in the Censuses? Where do they live? Does a widowed mother or father live with any of them? And their occupations? Often sons followed in the occupation of their fathers. (Not always though of course).
Have you found any of the deaths of his children? Scottish death certificates after 1855 will give the name and occupation of the father (hopefully!)
Good luck!
