Well, in 1900, there is one unmarried John McFarland/McFarlin in Troup that is definitely old enough to have kids in 1906.
https://www.familysearch.org/ark:/61903/1:1:M3V6-ZK5
There are a couple others, that would only be 18 or 19, but possible. It's also possible their ages aren't exact on the census and they're a little older.
https://www.familysearch.org/ark:/61903/1:1:M3VX-T4F
https://www.familysearch.org/ark:/61903/1:1:M3V6-V9Y
There's a Lula Cox who would be 18.
https://www.familysearch.org/ark:/61903/1:1:M3VX-MHC
There's a Lula Cox who would be 16.
https://www.familysearch.org/ark:/61903/1:1:M3V6-NTD
There was also another Lula Cameron who married a John McFarland/McFarlin.
https://www.familysearch.org/ark:/61903/1:1:QLGY-GYQ3
Online, there doesn't seem to be a marriage record (I checked Ancestry too), or there is and it doesn't name their parents, which makes it hard to pinpoint which persons they might be on censuses. Do you know where John and Lou are supposed to have died? Death records might name parents, like this Lula Cameron/McFarland's does, and pinpoint which ones they are on censuses. Her parents are on the 1900 census.
I think you have some candidates, right in Troup, even more if you include surrounding counties, or the entire state. I don't think you need to hunt for Natives, maybe just better paper records for the area.