In the book "Jack: A Biography of Jack Nicholson" Brando's then girlfriend Pat Quinn says that once Nicholson moved in next to Brando, his behavior changed - they began sharing women.
Also from People Magazine "In 1995, 25-year-old Cheyenne, who had a history of drug use and mental problems, hanged herself in her mother's house in Tahiti, Brando's second home for many years. The distraught actor cut off relationships with many close friends after the tragedy, including onetime lover Pat Quinn, 61, an L.A. screenwriter and former actress. "He lost his daughter, whom he loved dearly," says Quinn. "He didn't know how to be with her. He didn't seem to have the gift." As for Christian's trouble, she says, it "just doomed them both."