(Guardian) - Eunice Kennedy Shriver, founder of the Special Olympics, younger sister of former president John F Kennedy, and mother-in-law of California's governor, Arnold Schwarzenegger, has died at the age of 88.

A statement from her family said she died in the early hours of this morning in hospital in Hyannis, Cape Cod. She had suffered a number of strokes in recent years. The town of Hyannis is closely associated with the Kennedy family and it has a museum commemorating JFK.

"We have always been honoured to share our mother with people of goodwill the world over who believe, as she did, that there is no limit to the human spirit," her family members said in a statement.

Shriver was noted for her charity work with children, and launched the Special Olympic Games in 1968, in which 190 countries now participate.

Her interest in working with mentally handicapped people was attributed to her closeness to her sister Rosemary, who underwent a lobotomy at the age of 23 – a then fashionable supposed remedy for mood swings and depression – that left her incapacitated for life. Rosemary died in hospital aged 86, four years ago, with her sister by her side.

Shriver was awarded her country's highest civilian honour, the Presidential Medal of Freedom, in 1984, and was still working daily at the head office of the Special Olympics into her late 70s.

In 1953, she married Robert Sargent Shriver, who became ambassador to France, the first director of the Peace Corps and an unsuccessful vice-presidential candidate in 1972.

Shriver was the fifth of nine children of the formidable Boston Irish politician and businessman Senator Joseph Kennedy, and his wife Rose. Her siblings included John, the president who was assassinated in 1963, and Robert, who was assassinated five years later.

Her youngest brother, Edward, is still a serving senator 47 years after he was first elected, despite battling a brain tumour. Her sisters include Jean Kennedy Smith, who served as US ambassador to Ireland under Bill Clinton, and her daughter Maria is married to Arnold Schwarzenegger.

So many tragedies befell her family that some nicknamed it the Curse of the Kennedys. Her elder brother Joseph, a pilot, was killed in the second world war; her sister Kathleen, who married into an aristocratic English family, the Devonshires, was widowed at 24 and died in a plane crash aged 28; Edward's career was overshadowed by the 1969 scandal when the car he was driving ran off a bridge at Chappaquiddick, drowning his passenger, Mary Jo Kopechne. John F Kennedy Jr, son of the president, died in 1999 when the plane he was flying crashed into the sea on the way to a family wedding at Hyannisport.