Harry Belafonte is 86, an age that tends to focus the mind on putting one’s affairs in order. And that is why, Mr. Belafonte says, he has filed a lawsuit in federal court against the three surviving children of one of his closest friends: the Rev. Dr. Martin Luther King Jr.

At issue are three documents that used to be in Mr. Belafonte’s collection of memorabilia, along with other photos and letters on the walls of his apartment, chronicling his long friendship with Dr. King. Mr. Belafonte says the papers were given to him by Dr. King himself; by his widow, Coretta Scott King; and by Dr. King’s close aide Stanley Levison.

Dr. King’s heirs — Dexter, Bernice and Martin Luther King III — have said the documents were taken without permission and belong to the estate.

Mr. Belafonte, who often supported the King family financially during the civil rights struggle, said the dispute pains him. He said in his view, Dr. King’s children had drifted away from their father’s values. “The papers are symbolic,” he said. “It’s really about what happened to the children, and I feel that somewhere, in this one area, I really failed Martin.”