Linda, I believe that Polly is Charles' sister.Some elder family members have said that there were only two children, Charles and a sister.But no one seemed to know her name. Ruth Smith stated in a letter to Jack Bethany in 1986 that Aunt Ollie's oldest daughter, Lessie, told her it was Mary Louise.Lessie was 92 at the time.(Info from Jay Bethany)So the Mary (Polly)fits, but the middle name, Louise, doesn't fit with one marriage record that gives her middle initial as "A".Either one could be wrong. I have no real proof yet, but I think she is probably his sister.Bill Cooper may have something more on this, as I understand he has Ruth's research.
I also think the name Henderson is significant and may have been their mother's maiden name.
Also, I have a question about your dates.Should the date for Western Grove, Newton Co., AR be 1862 instead of 1852 since they married in AL in 1855?