Article continues below advertisementAmong the many tragedies to plague the Kennedy family is the story of Mary Richardson Kennedy - and now, haunting new details are shedding light on the turmoil that defined her final days.An upcoming biography, RFK, Jr.: The Fall and Rise by Isabel Vincent, pulls back the curtain on Mary's unraveling marriage to Robert F. Kennedy Jr., exposing a deeply troubled relationship marked by addiction, alleged infidelity, emotional strain and a bitter divorce battle.