Eunice Kennedy Shriver, shown in this May 2005 file photo, is survived by her husband, former Peace Corps director R. Sargent Shriver, who has Alzheimer's disease. (Manuel Balce Ceneta/Associated Press)

Eunice Kennedy Shriver, the co-founder of the Special Olympics and sister of former U.S. president John F. Kennedy, has died at age 88, her family said Tuesday.

She died at 2 a.m. local time in Cape Cod Hospital in Hyannis, Ma., surrounded by her family, including her daughter, Maria Shriver, and the former journalist's husband, California Gov. Arnold Schwarzenegger.

"She was the light of our lives, a mother, wife, grandmother, sister and aunt who taught us by example and with passion what it means to live a faith-driven life of love and service to others," said a statement on Kennedy Shriver's official website.

Kennedy Shriver had suffered a series of strokes in recent years and had been in critical condition at the hospital since last week.

Kennedy Shriver was one of nine children of Joseph and Rose Kennedy. Among her noted siblings were brother John, the slain U.S. president. Her brother Robert served as attorney general and in the U.S. Senate before his run for the presidency and assassination, and a third brother, Edward, has been a senator since 1962.

She was one of the co-founders of the Special Olympics and was well known for helping people with mental disabilities.

'Extraordinary woman': Obama

Senator Ted Kennedy, who is battling brain cancer, said in a statement that even as a child his sister had a "boundless passion to make a difference."

"Though the Special Olympics will be her enduring monument, in our family she'll be remembered as a loyal and loving sister, a treasured wife to Sarge, and a wonderful mother and grandmother," he said.

Schwarzenegger said his mother-in-law "changed my life by raising such a fantastic daughter, and by putting me on the path to service, starting with drafting me as a coach for the Special Olympics."

U.S. President Barack Obama praised Kennedy Shriver on Tuesday as an inspiring mother, supportive wife and loving sister.

"But above all, she will be remembered as the founder of the Special Olympics, as a champion for people with intellectual disabilities, and as an extraordinary woman who, as much as anyone, taught our nation — and our world — that no physical or mental barrier can restrain the power of the human spirit," said the statement from the White House.

Won Medal of Freedom

Kennedy Shriver earned a sociology degree from Stanford University before taking a job as a social worker at a women's prison in West Virginia. She also worked in a Chicago juvenile court before taking over the Joseph P. Kennedy Foundation with the goal of improving the treatment of people with mental disabilities.

She ran summer camps on her family's estate for children with mental challenges, events inspired by her older sister, Rosemary, who died in 2005. Rosemary was said to have been mildly mentally challenged and spent much of her life in a long-term care facility in Wisconsin after undergoing a lobotomy at age 23.

The first Special Olympics, which took place in 1968 in Chicago, drew more than 1,000 participants from 26 U.S. states and Canada. Held every four years, the Games now draw thousands of competitors from 150 countries.

Kennedy Shriver was the recipient of numerous honours, including the United States's highest civilian award, the Presidential Medal of Freedom, which she received in 1984. In May, the National Portrait Gallery installed a painting of her — the first portrait commissioned by the museum of someone who had not been a president or first lady.

She has two surviving siblings: sister Jean Kennedy Smith and Ted Kennedy.

Kennedy Shriver is survived by five children: Maria; Timothy, chairman of the Special Olympics; Bobby, a city councillor in Santa Monica, Calif.; Mark, an executive at Save the Children; and Anthony, founder and chair of Best Buddies International, a volunteer organization for the mentally disabled.