For those following the discussion on TMG-L, here is the census enumeration in question.
Notice that Mary Lannom (indexed as Lamon) is dwelling 108, household 116. Her son Simpson is dwelling 108, household 117.
Her son John is dwelling 109, household 118.
Though Family Search has indexed this name as Lamon, if you look a t the record, you can see that it easily could be Lannom (the way the family spelt the name) or Lannon.
Notice that Sarah is listed as a wife, giving her relationship to John as HOH and not Mary. Simpson has no relationship given, nor does Mary.