Here is a 1900 Census record that matches the Wiley and Nancy at FindaGrave. Their oldest son is Charles F Fortner, born 1881.
"United States Census, 1900," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:M3Z6-FH7 : accessed 23 August 2018), Will Fortner, Davis Township (all west of Johnson Creek excl. Higginsville city), Lafayette, Missouri, United States; citing enumeration district (ED) 148, sheet 11B, family 197, NARA microfilm publication T623 (Washington, D.C.: National Archives and Records Administration, 1972.); FHL microfilm 1,240,869.
Also a Wiley Fortener, who served the Union. I think it says 73rd Illinois Infantry.
"United States Census of Union Veterans and Widows of the Civil War, 1890," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:K83S-468 : 11 March 2018), Wiley Fortener, 1890; citing NARA microfilm publication M123 (Washington, D.C.: National Archives and Records Administration, n.d.); FHL microfilm 338,191.
In 1860, living with a Stamper family. Could Dorcus be his sister?
"United States Census, 1860", database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MH8W-43X : 14 December 2017), Wiley Fortner in entry for John Stamper, 1860.
In 1850, living with the same family, but in Tennessee:
"United States Census, 1850," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MCDW-TPG : 12 April 2016), Wiley Fortner in household of John W Stamper, Bradley county, Bradley, Tennessee, United States; citing family 842, NARA microfilm publication M432 (Washington, D.C.: National Archives and Records Administration, n.d.).
As you said, there is more than one man with that name, though.