Martin Luther Keplinger was born on January 25, 1847, in Franklin, Illinois, to Samuel Keplinger and Permelia Green. His father was a farmer who owned $16,500 of real estate and $1,800 of personal property by 1860. He grew up and attended school in Franklin, and by 1870, he was working as a lawyer in Bloomington, Illinois.
He married Mary E. Ayers on February 24, 1880, and they had at least six children: Cora, born around 1880; Clara, born around 1882; Ruth, born around 1887; Wilkin, born around 1889; Nelly, born around 1891; and Laura, born around 1897. They lived in Carlinville, Illinois. He died there on January 10, 1929.