Rosemary Kennedy, the mentally disabled sister of the late President John F. Kennedy, has died at the age of 86.

The Kennedy family says in a statement that Rosemary Kennedy died Friday in Wisconsin with her three sisters and her sole surviving brother, Sen. Edward M. Kennedy, at her side.

Rosemary Kennedy was born in 1918 with a mild form of mental retardation, and her condition worsened significantly after a brain operation, or lobotomy she underwent at the age of 23. She lived most of her life at a school in the state of Wisconsin that specialized in care for the mentally disabled, but her mental disability was not widely known until her older brother, John, was elected president in 1960.

The statement released after Ms. Kennedy's death says her condition inspired many other family members to work to help the disabled. Her younger sister, Eunice Kennedy Shriver, founded the Special Olympics movement for disabled athletes.

Some information for this report provided by AP.