I have been researching this Knable family as I descend from William Knable a son of George Knable and Susannah Levering.Much of the Knable information I see on the web comes from a book "The Levering Family; A genealogical Account of Wigard Levering and Gerhard Levering, two of the Pioneer Settlers of Roxborough Twn PA, and their Descendants" by Joratio Gates Jones dated 1858.You would expect a book writen that long ago and closer to the facts would be correct, but I have found what I believe to be errors.
As for Rebecca Knable, daughter of George and Susannah, the book says she married Jacob Martin and lives near Oldtown MD, however, I just found this entry in "Portrait and Biographical Album of Johnson and Pawnee Counties Nebraska" : Job Armstead. Among the prosperous well-to-do citizens if Loncoln precinct is the subject of this sketch, whose beautiful farm of 150 acres of tillable, fertile land is situation on section 22, township 5 north, range 12 east.He is a native of what is now Fulton County, PA, and was born Jan 14, 1827 to Jacob and Rebecca Knable Armstead, both natives of Pennsylvania, but of Scotch and German extraction.....An uncle, Enoch Knable, was also a soldier and served through the Black Hawk War, while yet another uncle, Daniel Knable, fought in the Seminole Indian War in Florida."There is much more, but this indicates that Rebecca Knable married an Armstead and moved eventually to Nebraska.
I think the Jones book may also be incorrect on Enoch Knable, a brother to Rebecca.That book states that he died in 1836 in Seneca Co Ohio, but I find an Enoch Knable in Crawford County Ohio through the 1880 census.