I have 15 original letters written by John Hill Ferguson, Sr from Scotland to his sons in US 1850-1876.

I have written a book on this family's history. You have most of the children correct but some names that you list have not been found by me.
A bio of George Washington Ferguson Sr (IL) said that there were 12 children. Three died as infants (possibly the names you have but I don't have any proof--do you?). The others (including my gggrandfather) are Letitia (1822-1898), Geo.W. (1823-1911), William (1826-1862), John Hill, Jr (1829-1910), Thomas Millar (his mother's maiden name 1831-1875), Andrew (1834-1887), Joseph (1835-1861), James W. (1836-1897), Mary Ann 1841-1930).