Colin, just to recap for me!
Robert Aitken, your wife's direct line, was the son of James Aitken and Martha Houston? Have you been able to confirm this with his death reg (post 1855?)?
James Aitken and Helen Anderson (m. 1791 Barony) were the parents of Rev James and William who died at Hawthornbank in 1878. Some of their children include William b. 1793, Jean b. 1796, Alexander b. 1799, James b. 1802 and Helen b. 1805. All births in Barony.
We can now ignore this couple and their children?
So, some of the children to James and Martha include:
William b. 1797 Paisley
Hugh b. 1799 Inveresk
Agnes b. 1802 Glasgow
James b. 1805 Glasgow
John Hutchison b. 1807 Glasgow
Margaret b. 1809 Kilmarnock
Robert b. 1811 Kilmarnock...confirmed in the OPRs as 7th child
Marrion b. 1815 Kilmarnock
Monica