I don't know for sure, but according to the image of the marriage on Family Search Susannah and George Knowlton were married by Ezra McKee JP. Its possible Ezra was her father or possibly her uncle. Ezra was the son of David and Martha Dunlap McKee. At least two of Ezra's brothers, Robert and John, had a daughter named Susannah. Robert's was older and married Alfred Ogle in 1837 in Morgan county and John's was about the same age but was still living with him in the 1850 census, so not the same one. Trees online don't show a daughter Susannah for Ezra or the other brothers, but since Susannah was married before 1850 families may not know of her.