The quartet consisted of Donald (lead tenor vocals, April 29, 1915 – November 13, 1999), Herbert (tenor vocals, April 2, 1912 – April 12, 1989), Harry (baritone vocals, August 9, 1913 – June 28, 1982), and John Jr. (guitar, double bass, vocals; October 19, 1910 – January 23, 1936).
Their father, John Hutchinson Mills (February 11, 1882 – December 8, 1967), was a barber with his own shop and a barbershop quartet. He was the son of William Hutchinson Mills and Cecilia Simms who lived in Bellefonte, Pennsylvania.
As the boys grew older, they began singing in the choir of the Cyrene African Methodist Episcopal Church and in the Park Avenue Baptist Church in Piqua. After lessons at the Spring Street Grammar School, they gathered in front of their father's barbershop or on the corner to perform. They entered an amateur contest at May's Opera House but while on stage Harry realized he had lost his kazoo. He improvised by cupping his hand over his mouth and mimicking the sound of trumpet. The brothers liked the idea and worked it into their act. John, the bass vocalist, would imitate the tuba. Harry, a baritone, imitated the trumpet, Herbert became the second trumpet, and Donald the trombone. John accompanied the four-part harmony on ukulele and then guitar. They practiced imitating orchestras they heard on the radio.