Miles, it's great you got an original of the marriage certificate. Excellent work.
May I respectfully beg to differ with your conclusion, though? You apparently ordered a copy of a marriage certificate for a William Lowe getting married to a Mary Sanderlin in Jefferson County, Ohio, in 1828. (I am guessing you are referring to a copy you got in the mail, as the transcription of it was earlier posted). But that document alone does not prove this is YOUR William and Mary. There was more than one William Lowe and more than one Mary that your William Lowe could have married. What was needed was a tie from that marriage, to the couple living with a son David in Green County, Wisconsin, in 1850.
The fact that a William Lowe lives next door to a Thomas Sanderlin for so many years is a clue that they might be family.
The fact that a Susan Sanderlin age 8 and apparently an orphan lives with Mary Lowe is a clue that they might be family.
The obit for David's sister makes the final connection - William's wife is indeed Mary Sanderlin, and you have their marriage certificate - a treasure.
Just letting you know how my brain works and hope you don't mind. Let me know if I'm off base here.