A play about the life of Aristotle Onassis suggesting the Greek shipping tycoon was behind the death of Robert Kennedy is fiction, family members said.

The play "Onassis" at London's Novello Theater dramatizes the relationships Onassis had with Jacqueline Kennedy and Maria Callas, and is based on a 2005 book by Peter Evans, The Daily Telegraph reported.

The shipping magnate died in 1975, and the charity he founded, the Onassis Foundation, released a statement defending his reputation.

"The Onassis Foundation does not wish to comment on Mr. Evans' fiction or the play based on it. It is forced to underline, however, that Mr. Evans' book is not a biography, and not even written with the permission of Aristotle Onassis. From what we know, such permission has never been granted to Mr. Evans.

It continued, "It is not based on serious research, but on rumors flying about Aristotle Onassis. It is no coincidence that it was published many years after the death of Onassis himself and all the witnesses cited by the author."

The play suggests Onassis wanted U.S. Sen. Robert Kennedy killed because he opposed the marriage of Onassis and the late president's widow.

The play opened last week to mixed reviews.

It is "a pretentious modern-day Greek tragedy" one reviewer said, adding that the wig worn by the lead character appeared "lovingly crafted from recycled Brillo pads."