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.
While in separate prisons, they couldn't talk on the phone, but they did write letters to each other and would play chess by sending moves to each other through snail mail, Rand said.
Now, if they wish, they can spend time together at meals and during recreational and exercise periods as they continue serving out their lifelong sentences.
Their father, Jose Menendez, a successful Cuban-American business executive, was shot point-blank in the head.
The widely-watched double murder trials, including a mistrial, of Erik Menendez, 47, and Lyle Menendez, 50, gripped the country during the 1990s. They shot their mother several times in her chest and face. Prosecutors said there was no evidence of the claims and instead contended the killings were about greed and wanting access to their parents' fortune.
The siblings were convicted in 1996 of murdering their parents inside their Beverly Hills mansion on On August 20, 1989.
A spokeswoman for the California Department of Corrections and Rehabilitation confirmed with CNN that Lyle Menendez requested to transfer to his brother's prison in San Diego in February and finally placed in the same housing unit on Wednesday.
Their first trials ended in mistrials, but at the end of a second trial in 1996, the brothers were convicted of first-degree murder and sentenced to two consecutive life prison terms without the possibility of parole.
Thornton said while she couldn't confirm whether the brothers had made contact by Thursday afternoon, they likely were in contact in other ways over the last 22 years.
She said Erik was "settling in" and that the brothers already had enjoyed a "heartfelt reunion".
They were arrested months later after one of the brothers allegedly confessed to a psychologist and the other threatened to kill the doctor, thus voiding doctor-patient confidentiality agreements.
However, the brothers lived in separate housing units and wouldn't have seen one another since the prison houses almost 3,900 inmates.
Rand said the last few years Lyle told him that he "missed his brother so much. So this is just an overwhelming, emotional, happy moment for not only the brothers but their entire family".