My wife's grandfather's letters (from 1928) indicate that James Calderwood died in 1770, and had a brother named William. He had traveled to Calderwood Castle, and must have picked up that piece of information from the locals.
I didn't know that James wife was named Margaret. Do you by any chance know where (my branch) of the Calderwood name became Catherwood. My father, age ninety, never told me, and now, can't remember. Tradition has it that the name Calderwood originally came from the Roman Caldarius, who, in 87 a.d. was given the lands that that are now Polton, outside of Edinburgh.