2018 collection. Sister Sledge was a musical vocal group from Philadelphia, Pennsylvania. Formed in 1971, the group consisted of sisters Debbie, Joni, Kim and Kathy Sledge. Symbolizing strong family values, the siblings achieved international success at the height of the disco era. The year 1979 saw the release of their breakthrough album We Are Family, which peaked at number three on the US Album Chart and went Platinum. The album included the 1979 single "We Are Family" which reached number two on the US Billboard Hot 100 and earned them a Grammy Award nomination, together with two other 1979 top 20 international hits "He's the Greatest Dancer" and "Lost in Music". Other international hits include "Mama Never Told Me" (1973) and "Thinking of You" (1984).