Hi Russ,
There were eight children born to George and Marion.
In the 1841 census the eldest three, Ann, Robert and Donald, are listed.
In 1851 Robert, Donald, Esther, Alexander, John, William are listed. Ann is obviously away working somewhere else.
Lastly Jessie was born just after this census.
No Mary in the census records for this family.
I know the family tree you are referring to. It is extensive but does have one or two errors.
Regards
Adair