Jemima C. Bay was born on November 16, 1846, in Ohio to Joseph and Sarah Bay. Her father was a farmer who owned $500 of real estate and $50 of personal property by 1860. The family lived in Perry, Ohio, until the 1850s, when they moved to Thorncreek, Indiana. In the 1860s, they moved to Plain, Ohio.
She married Daniel Hiner on September 26, 1872, and they had at least six children: Mary, born around 1875; Daniel, born around 1875; Lucy, born around 1879; Harvey, born around 1881; Clara, born around 1884; and Jennie, born around 1889. They lived in Plain, and her husband worked as a farmer. She helped care for her elderly mother until at least 1880. Her husband died on August 31, 1902, and she remained in Plain with her children. She died there on December 22, 1911.