Born: April 18, 1859, Washington County, Pennsylvania.
Died: December 7, 1931, Washington County, Pennsylvania.
Buried: Allegheny Cemetery, Pittsburgh, Pennsylvania.
Jennings was the son of Robert Allen Jennings, Sr., and Julia Ann Weber. He married twice, to Elizabeth Margaret White (1881) and Julia Caywood Murdock (1920).
He was a professor of music, and member of the West Washington Methodist Episcopal church in Pittsburgh. He was widely known as a song leader, and often assisted in that role in evangelistic services. He is said to have been associated with Gypsy Smith for some years.