At this point I cannot prove that Isaac is the father of Jacob.  Some sources cite a David Nutter as his father.  Neither was he married to Martha Greathouse.  However, they did have a son together, Charles Clayton Nutter.  Upon the death of Martha's father, her mother, Sarah Starcher, married Levi Nutter, who became Martha's stepfather.  Levi reared her son Charles Clayton Nutter as his son, but he was actually the grandson of his wife Sarah.  After Sarah's death Levi went to live with Charles and his family, and he (Levi) is listed in the 1900 and 1910 census records as Charles grandfather.