I have had a look in the Irish statutory marriage records for the 3 couples you have named but can’t see any likely matches. The records start in 1845. Can you give us some dates for when they likely were born, married or died? Did any of them die in Ireland? What denomination were they?
The Scottish marriage certificates you have found should show the parents occupation(s) plus whether they were alive or dead on the date of the marriage. That information would be helpful too.