There is a 20 yr. gap in the census records [1880 - 1900] as the 1890 census was burned in the 1920's. Add 20 yrs to everyone's 1880 age for the 1900 census.
I’m not related to any member of this family.
1850, 1860 & 1870 census records do not show family relationships, marital status or parental birthplaces.
Step children are not enumerated as “step” children
Adopted children are not enumerated as “adopted”
Grand children are not enumerated as “grand children”
Orphaned children were not enumerated as "orphan"
Immigration date is not recorded
1850 is the 1st census that shows all family members with their birthplaces
1880 is the 1st census that shows parental birthplaces and family relationships +++
ILLINOIS did not issue death certs. until 1916.
Name: John Nichols
Age in 1870: 9
Birth Year: abt 1861
Home in 1870: Sellers, Hardin, Illinois
Post Office: Sellers Landing
James Nichols 55, ILL - farmer
Elander Nichols 55, TN 
Alex Nichols 24, KY
James Nichols 20, ILL
John Nichols 9, ILL 
WHO did John Nichols 9, ILL  marry??
Need her 1st name +DOB + birthplace.
Need 1st names for ALL children + DOB' + birthplaces.