But the brothers lived in separate housing units and would not have seen each other, Thornton said.
In the sensational televised trial, the brothers, then teenagers, claimed they killed their parents, Jose and Mary Louise Menendez of Beverly Hills, California, after years of sexual abuse by their father.
Two brothers who killed their parents almost 30 years ago have been reunited in a California prison this week.
They were sentenced to two consecutive life terms without the possibility of parole in 1996 after their first trial ended in a hung jury.
No evidence of molestation was ever found.
That changed Wednesday, when Eric moved into the same housing unit as his brother, a unit where inmates agree to participate in educational and other rehabilitation programs without fighting or creating disruptions.
Their mother died after suffering 10 shotgun blasts to several parts of her body.
They were arrested after the girlfriend of a psychologist that had been treating Erik Menendez went to police to say that he had physically threatened the doctor. Lyle Menendez was previously housed at Mule Creek State Prison near Sacramento but was relocated to the San Diego prison in February after his security classification was lowered. Prison officials said then that they often balked at putting partners in crime together, and the Beverly Hills detective who investigated the slayings argued that the brothers might conspire to escape if they were together.
After spending 22 years apart, the homicidal brothers will now be able to see each other every day during meals and exercise breaks, prison officials said.
According to Robert Rand, a journalist who has covered the case since 1989 and was a consultant for a 2017 television programme about the brothers, the pair both "burst into tears immediately" upon their reunion.
But they reportedly wrote letters and played chess by sending their moves through the mail, according to Mr Rand. Erik Menendez, who was already a prisoner at Donovan, was moved this week from his unit to the one his brother is in.
"I love my mother, and I still cry over my mother, and I don't forgive her", he told the "Today" show in September. "What kind of mother lets it happen?"