My husband's Kelley/Kelly line was spelled both ways on headstones & documents. The early ones [late 1700's-1860's] was mostly Kelly. During the Civil War, his great-grandfather's paperwork was spelled both ways. He couldn't read or write. His family from then on spelled it KELLEY, his siblings spells it KELLY to this day. As far back as we have traced the family, they were all Baptist. Most of the spellings got changed because people couldn't read or write. We have talked to many people who spell their last name one way and a cousin spells it another way.