Members of the family that owns OxyContin maker Purdue Pharma won’t contribute billions of dollars to a legal settlement unless they get off the hook for all current and future lawsuits over the company’s activities, one of them told a court Tuesday in a rare public appearance.David Sackler, grandson of one of the brothers who nearly 70 years ago bought the company that later became Purdue, testified at a hearing in federal bankruptcy court in White Plains, New York, that unless the settlement is approved with those …