Answer:
Out of all the children of John and Jackie Kennedy she is. But she is not the only member of the Kennedy family that is still alive.
Many of Robert Kenendy's children are still alive and have children
RFK Jr
Rory
Kathleen
Micheal (who has since past on-but had several children by Kathy Lee Gifford's step-daughter)
Kerry Kennedy-who was married to NYS Atterney General Andrew Cuomo
Patrica Lawford's children are still alive and have children
Christopher Kennedy Lawford is one
Eunice Shriver's children have children-one of which is Maria Shriver who has four children with Arnald Schwartzeneger.
Jean Kennedy Smith had several children
Ted Kennedy had children and his son Ted Jr has children as well.