I wish to correct the previous post about St John Thornhill of Kildorrery. Apparently, it is highly unlikely that he was born in England as I thought, but in Ireland and before 1798 (date taken from his death record, age at the time of his death was given as 75). However, he did marry Elizabeth Courtney in 1817 and had seven children. He was also the landlord of properties in Kildorrery and tenant of properties in Kildorrery and Farahy.
Thank you for your help.