I guess I should put my 2 cents worth into this discussion.
Robert's father was in fact Charles Rattray not William. I have been able to confirm this with Robert and Sarah's marriage details. He died 7-3-184 of Inflamation. He was married to Elizabeth Brydon b 1803 died 8-11-1874 and they had 3 children John, Robert Brydon and William B.
Robert Brydon Rattray 1838 was married to Sarah Beattie. He died 2-8-1910 of Influenza & pneumonia and they had 7 children Charles Brydone, Bary Beattie, Robert Beattie, Robert Beattie (Bryden), John (Jock) Beattie, Elizabeth (Lizzie) and Helen Muir (Nellie).
