Ooh, that's interesting! I didn't know about the naming convention; that could be an interesting lead. Also explains why so many people in my family have the same name.
I'm not sure where Daniel would have been for the 1861 census, or why Isabella would have been listed with her parents. He died at age 55, so there doesn't seem to be a lot of records for him related to his children. I haven't had a great time finding information on his children either, other than my direct relative (Archibald Cuthbert Grant). In the records I have found, it only mentions Daniel and Isabella's names - not any real detail.