The sister of President Kennedy and mother of Maria Shriver was 88

Eunice Kennedy Shiver, the younger sister of President John F. Kennedy and the mother of California First Lady Maria Shriver Schwarzenegger, died at around 2 a.m. Tuesday, her family has announced.

She was 88 and the cause of her death was not disclosed, though for the past week she was listed in critical condition at Cape Cod Hospital in Barnstable, Mass., where family members, including the Schwarzeneggers,, had gathered.

In a statement, the family called Shriver “a living prayer, a living advocate, a living center of power. She set out to change the world and to change us, and she did that and more.” Younger brother Sen. Edward Kennedy also paid tribute to her “great humor, sharp wit and … boundless passion to make a difference.”

Shriver organized the first Special Olympics in 1968, inspired in part by the struggles of her mentally disabled sister, Rosemary. Shriver’s son, Tim, now runs the Special Olympics, and her husband, Robert “Sargeant” Shriver, Jr., the first director of the PEace Corps, also survives her, along with their five children and 19 grandchildren.

Earlier this week, the Boston Globe reported that Pope Benedict XVI was “holding close to his heart Eunice as she is called home to eternal life.”