A little more digging indicates that William Harrison Lott, Sr. probably had a first wife Velma A. Parton. They had no children that I can find and she died in 1930. He would have then married Mammie Lucille Ivey and had William Harrison Lott, Jr. in 1935.
1910 census lists Emmer S. Ivey, wife of William G., in Hunt County. Her birthplace given as Tennessee. Don't know if this could be your Lucille's parents.