SMITHFIELD — For Johnston County Registrar of Deeds Craig Olive and his blended family, Alzheimer’s disease is personal. He and his kin have seen the disease ravage parents, siblings, grandparents, aunts and uncles. Olive lost his mother, Pearl Thompson Brown Olive, to Alzheimer’s in 2007. “She helped raise 15 children altogether — stepchildren and her own,” he recalls in an interview from his office in the Johnston County Courthouse. But Pearl was more than his mom.