The father of Beyoncé and Solange Knowles, Mathew Knowles, revealed that he has been diagnosed with breast cancer. In a Good Morning America interview with Michael Strahan slated to air Wednesday, the 67-year-old opens up about his battle with cancer for the first time. “How was it to tell your family about the diagnosis?” Strahan asks in a teaser clip. Knowles was the manager for Destiny's Child, an iconic girl group Beyoncé took part in before launching her solo career. He also managed both Beyoncé and Solange Knowles at points in their careers.