Sister Sledge is an American musical group from Philadelphia, Pennsylvania. Formed in 1971, the group was originally composed of sisters Debbie, Joni, Kathy and Kim Sledge. With Kathy leaving in 1989 the group have since operated as a trio (with Kathy occasionally re-joining for one-off performances and several releases in the 1990s). Having enjoyed marginal success in Europe during the middle of the decade, mainstream success was achieved when breakthrough album We Are Family was released in 1979.