This is not going to help sort out your dilemma, but I think you may have names mixed up. Nathan Armstrong married Cursa/Coursey/ Cursy Charlotte Franklin.
There are numerous census records of this couple as well as other records. They had a son Isaac b. abt 1863. No son Nelson. I wasn't able to find a wife for Isaac other than the last name on Nelson's death record. It doesn't seem possible that Nelson is the son of Isaac, and he is not listed as a child of Cursa and Nathan?
Alabama, Marriages, 1816-1957
Citing this Record: "Alabama, Marriages, 1816-1957," index, FamilySearch (https://familysearch.org/pal:/MM9.1.1/FQ9N-KZ3), Nathan Armstrong and Coursey Charlotte Franklin, 01 Apr 1860; citing reference ; FHL microfilm 1034797.
Name: Nathan Armstrong
Spouse: Coursey Charlotte Franklin
Marriage: 01 Apr 1860 Blount, Alabama
U S Census, 1900 Precincts 19-20 Walker, Bangor, Blount, AL
Citing this Record: "United States Census, 1900," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/M9Z5-JQ6 ), Isaac Armstrong, Precincts 19-20 Walker, Bangor, Blount, Alabama, United States; citing sheet 4A, family 56, NARA microfilm publication T623, FHL microfilm 1240003.
Isaac Armstrong Head M 37 Oct. 1863 White married 14 years (No other members in this household?)
U S Census, 1880 Township 13 Range 2 West, Blount, AL
Citing this Record: "United States Census, 1880," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/M4JM-N8P ), Isaac J Armstrong in household of Nathan Armstrong, Township 13 Range 2 West, Blount, Alabama, United States; citing sheet 486B, NARA microfilm publication T9.
Nathan Armstrong Self M 47 AL
Cursa C Armstrong Wife F 38 AL
Asham J Armstrong Son M 19 AL
Isaac J Armstrong Son M 16 AL
Taylor A L Armstrong Son M 8 AL
Nancy M Armstrong Dau F 6 AL
Sarah M Armstrong Dau F 4 AL
Nathan T Armstrong Son M 2 AL
Emley S Armstrong Dau F 0 AL
Willie Franklin Bro-in-law M 17 AL
Frances C Elliot Niece F 3 AL
William M Armstrong Son M 14 AL
Mary E Armstrong Dau F 12 AL
Daniel D Armstrong Son M 10 AL
U S Census, 1870 Township 13 Range 2 West, Blount, AL
Citing this Record: "United States Census, 1870," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/MHVP-YBD), Nathan Armstrong, Alabama, United States; citing p. 4, family 21, NARA microfilm publication M593, FHL microfilm 000545502.
Nathan Armstrong M 39 Alabama
Charlotte Armstrong F 27 Alabama
Jesse Armstrong M 10 Alabama
Matilda Armstrong F 9 Alabama
Isaac Armstrong M 7 Alabama
Elizabeth Armstrong F 4 Alabama
Daniel Armstrong M 1 Alabama
U S Census, 1860 Sub Div No 1, Blount, AL
Citing this Record: "United States Census, 1860," index, FamilySearch (https://familysearch.org/pal:/MM9.1.1/MHDC-HYG ), Nathan Armstrong, Sub Div No 1, Blount, Alabama, United States; citing "1860 U.S. Federal Census - Population," Fold3.com; p. 60, household ID 410, NARA microfilm publication M653; FHL microfilm 803002
Nathan Armstrong M 25 Ala
Charlott Armstrong F 18 Ala
More on Cursa/Cursey/Kersey Charlotte/Lottie and Nathan:
https://familysearch.org/search/record/results?count=20&query=%2Bgivenname%3A%22cursa%20charlotte%22~%20%2Bsurname%3Aarmstrong~%20%2Bbirth_place%3Aal~%20%2Bbirth_year%3A1840-1849~%20%2Bspouse_givenname%3Anathan~%20%2Bspouse_surname%3Aarmstrong~%20%2Bfather_surname%3Afranklin~&gender=F