You posted a long time ago in relation to this. I am researching my mother's side of the family.
I believe that David born in 1854 was my great great great grandfather. He married Margaret Robb in 1873.
I am at the stage where I have now come across James, who I understand would be my gggg grandather.
If you are still interested in this, perhaps you could get in touch? It would be good to share info with you.