Henry Gragg 1755/Nancy Crow

I have a handwritten letter by Sarah Jane Weger(1829-1913) that her parents were Thomas Gragg Weger (1803) and Catherine Baugher (1813).  I believe Thomas Gragg Weger's parents were William E. Weger(1780-1833) and Elizabeth Gragg (June 1773).  I have no proof of that nor that Elizabeth's father was Henry Gregg who was married to Nancy Crow.  Thanks for help.