First, I've never lived in Knox County or Vincennes. My branch of the Purcell family arrived in that area c. 1790 - 1800. Most were from Hampshire County,, WV and the earlier settlers in Knox/Vincennes were born in WV (then VA). Some stayed, many emigrated westward or to other parts of the expanding nation.
Sarah Decker, for example, was born 11/23/1778 in Hampshire County. She was the daughter of John Decker and Hannah Harness. John was born in Hardy County, WV around 1750, His wife Hannah was born around 1755 (also in Hardy, WV). However, I have a copy of a will indicating John was married to Dinah. This may indicate a second wife or that the Will was written by another John Decker altogether.
The Decker side of the family is primarily of Dutch origin.
Sarah Married Noah Dunlap Purcell, which makes her my fourth great aunt.
You need some dates to go with your data and I need to do more research