Former first lady Rosalynn Carter died Sunday at 96 . The wife of President Jimmy Carter for 77 years, she is being remembered for her roles as an adviser to the president and as an advocate and humanitarian in the decades after the Carters left the White House. And as her legacy is being remembered, a unique, little-known relationship is also being remembered: Mrs. Carter’s decades-long advocacy for and friendship with Mary Prince, a Black woman who went being wrongfully convicted of murder to becoming a nanny for the Carters’ children and a lifelong friend to the former first lady.