I realize there haven't been any posts to this thread in some years, but I just recently began researching the Jack family and can contribute some new information.
My interest started with William Jack/ Margaret Morton.
Margaret was the daughter of James Morton/ Margaret Lyon, born 1748, Bells Dyke New Monkland. Her sister Janet married William Main 1775, New Monkland. William was a descendant of John Main of Ballochney (my line).
James Jack, son of William Jack/ Margaret Morton, married Catherine Taylor, 1805, Shotts.
They had the following children in Shotts: William 1806 (Janet Walker 1843); John 1807 (Janet Allan 1845); James 1810 (Margaret Hill abt 1836); Thomas 1811; Marion 1814; Margaret 1816 (William Hill 1838); Catherine 1819; Jane 1821-1905 (Alexander Mackie 1840); Ann 1823; George 1826.
In the 1841 census; James Jack 60, farmer, Wester Braco Shotts; John 30; George 15; Ann 7.
There are a number of important connections for me with this family.
William Jack married Janet Walker; after William died, Janet married John Main, another in the John Main of Ballochney line.
The Hills, Margaret and William, were the children of George Hill/ Jean Jack.
George Hill was the son of Lodovick Hill/ Isobel Main (who also descended from the John Main of Ballochney line). I'm not sure who were the parents of Jean Jack.
A question for Richard: In the OPR birth record of John Jack, there is a partial notation above his entry with the name Agnes Main. Would you be able to find out whose birth record this was. Thanks. Jim Main