Both John and Margaret are in the 1841 census aged 55. In the 1851 census John is a widower aged 70, born in Arbory. He is not in the 1861 census and probably the John buried in Arbory on November 17 1854, age 75. She could be the Margaret buried in Arbory aged 57 on June 28 1843.
The closest christening for Margaret is on June 4 1786 to William Harrison and Isabel Taubman.
John left a will, which is transcribed on Brian's site. His eldest son was christened Thomas on March 15 1807. and his eldest daughter, Elizabeth on Feb 25 1810.
If they named their children after his father and her mother, this would suggest that Thomas Kinvig and Elizabeth Clague were his parents. But that would rule out Wlliam and Isabel as her parents. Elizabeth was buried in Arbory on March 2 1831. Both Thomas and Elizabeth left wills, which have not been transcribed, but which can be ordered and viewed at a local Family History Centre