The MILLERs and the LONGs are in adjacent Census records in Ellis County in 1860. Nancy Jane ROPER was married to William A. LONG. Nancy's sister Telete ROPER was married to Felix MILLER. Felix and Telete MILLER were enumerated in Hill County, Texas, in 1860.
I seriously doubt that this is a coincidence. Felix MILLER is very likely to be closely related to the MILLER family residing adjacent to the LONG family in 1860.