I have searched the Scot. OPRs as well as the IGI and haven't found Robert in either. I had been trying to identify him through the names of children and grandchildren. This is basically why I didn't accept the IGI entries. All my other Scots lines have used the patrynomic method of naming their children.

Mary's line is definitely East Lothian Scotland. Mary's parents are Walter and Anne (m 1783 Tranent E. Loth) Her siblings were Marion (b1786) and Margaret (b1788).

I wasn't sure about James Murray (b1814). He fitted in between the other children, but his mother's name was Marion and James was the only child to be given a second name. Robert was a sailor, and could have been at sea for long periods. This could account for the gap between Anne (b1812) and George (b1818) after Charles was born in 1810
Despite the many spellings used in other records, in this family's entries were always spelled Waterston. If this is not the Manx spelling, I'll be grateful for the Manx line I have and keep on searching.
Thank you for all your help