Sledge and her sisters formed Sister Sledge in 1971
Joni Sledge, who recorded the dance anthem 'We Are Family' with her three sisters, has died aged 60.
Sledge was discovered dead at her home in Phoenix, Arizona, by a friend on Friday.
The band's publicist, Biff Warren, said a cause of death has not been established and that Sledge had not been ill.
"On yesterday, numbness fell upon our family. We welcome your prayers as we weep the loss of our sister, mother, aunt, niece and cousin," the family said in a statement.
Sledge and her sisters Debbie, Kim and Kathy formed Sister Sledge in 1971, and had their breakout success with the album 'We Are Family' in 1979.
The title track was an infectious song that celebrated their familial connection with the refrain: "We are family, I got all my sisters with me."
The song, which was nominated for a Grammy, became an anthem of unity and women's empowerment.
Both the song and the album sold more than one million copies.
The sisters also had a hit with a cover of the Mary Wells song My Guy in 1982, but they would never duplicate the success they had in the 1970s.
While sister Kathy left for a solo career in 1989, the remaining members continued to perform and record, including a performance for Pope Francis in 2015.
They last performed together in concert in October. Sledge is survived by a son, as well as her sisters and other relatives.