More than a dozen family members of Erik and Lyle Menendez have called for the release of the brothers from prison after the killings of their parents in their Beverly Hills mansion 35 years ago.

“I had no idea the extent of the abuse they suffered at the hands of my brother-in-law. None of us did,” said Joan Andersen VanderMolen, Kitty Menendez’s sister.

“We know that abuse has long effects, and victims of trauma sometimes act in ways that are very difficult to understand.”

“The whole world was not ready to hear that boys could be raped,” she said, adding “today we know better.”

Lawyer Mark Geragos speaks in front of members of the Menendez family during a press conference (Damian Dovarganes/AP)

The news conference in Los Angeles was the largest gathering of the extended family since the brothers’ 1996 sentencing.

The public call for their release comes less than two weeks after the Los Angeles County district attorney announced his office would be reviewing new evidence to determine whether the brothers should be serving life sentences.

The brothers are currently serving life sentences in state prison without the possibility of parole.

Lyle Menendez, who was then 21, and Erik Menendez, then 18, admitted they fatally shot their entertainment executive father, Jose Menendez, and their mother, Kitty Menendez, in 1989 but said they feared their parents were about to kill them to prevent the disclosure of the father’s long-term sexual molestation of Erik.

Prosecutors at the time contended there was no evidence of any molestation. They said the sons were after their parents’ multimillion-dollar estate.

“They tried to protect themselves the only way they knew how,” said Brian A Andersen Jr, nephew of Kitty Menendez. “Instead of being seen as victims, they were vilified.”

“They are no longer a threat to society,” he continued.

Others in the family echoed similar sentiments.

Erik Menendez, centre, listens to his lawyer as his brother Lyle looks on in court in 1991 (Julie Markes/AP)

“If Lyle and Erik’s case were heard today, with the understanding we now have about abuse and PTSD, there is no doubt in my mind that their sentencing would have been very different,” said Anamaria Baralt, a niece of Jose Menendez.

While the group of relatives called for the brothers’ release, Kitty Menendez’s brother, Milton Andersen – who is 90 years old – said through a lawyer that he believes “the appropriate sentence” is life in prison without possibility of parole. Mr Andersen was not available for an interview.

“He believes that there was no molestation that occurred. He believes that the motive was pure greed, because they had just learned that they were going to be taken out of the will,” said Kathy Cady, Mr Andersen’s lawyer.

The extended family’s lawyer, Bryan Freedman, previously said they strongly support the brothers’ release.

“For years, I struggled to come to terms with what happened to my sister’s family,” Joan VanderMolen said.

District attorney George Gascon has said there is no question the brothers committed the 1989 murders, but after his office looks at the new evidence, prosecutors will make a decision on whether a resentencing is warranted in the notorious case that captured national attention.

The evidence includes a letter written by Erik Menendez that his lawyers say corroborates the allegations that he was sexually abused by his father. A hearing was scheduled for November 29.

Erik Menendez and Lyle Menendez (California Department of Corrections and Rehabilitation/AP)

The brothers’ lawyers said the family believed from the beginning they should have been charged with manslaughter rather than murder. Manslaughter was not an option for the jury during the second trial that ultimately led to the brothers’ murder conviction, lawyer Mark Geragos previously said.

The case has gained new traction in recent weeks after Netflix began streaming the true-crime drama Monsters: The Lyle and Erik Menendez Story.

But the brothers have said they killed their parents out of self-defence after enduring a lifetime of physical, emotional and sexual abuse from them.

Their lawyers argue that because of society’s changing views on sexual abuse, that the brothers may not have been convicted of first-degree murder and sentenced to life without parole today.

Jurors in 1996 rejected a death sentence in favour of life without parole.