EXCLUSIVE: Inside Murdering Menendez Brothers Prison Hell After They Were Attacked Behind Bars as Freedom Bids Keep Failing

The murderous Menendez brothers – who've been locked up for over three decades for fatally shooting their mom and dad at the couple's Beverly Hills mansion – were brutally attacked behind bars, the jailbirds claim.

Erik Menendez, now 54, said he and his sibling Lyle, 57, were assaulted by fellow convicts early in their incarceration after the 1989 shotgun slayings of their parents – José and Kitty Menendez, RadarOnline.com can reveal.

Erik explained: "Prison was hard for me. I faced a lot of bullying and trauma. It was a dangerous environment. I was picked on, bullied violently, and it was traumatic and it was continual."

The men are currently serving life sentences at Richard J. Donovan Correctional Facility in Otay Mesa, California. The brothers don't bunk together but are assigned to the same cell block – and staffers say the tight-knit twosome regularly socialize at lunch.

However, for their first 21 years as inmates, the killers were housed at different facilities.

Now, Erik is speaking out about the moment he learned of his older brother's beatdown.

He said: "I was told 'Lyle just got assaulted and got his jaw broken.' I'm thinking, ‘He's over there, I'm going through this over here, and at least we could protect each other maybe if we were together,' but we were not even allowed to be together."

Erik said he continually faced attacks – but silently vowed: "I'm not gonna fight back, I'm not going to engage."

He added: "I had no one really to turn to for help, and I was separated from Lyle."

The imprisoned pair claimed they killed their parents in self-defense after years of torturous sexual, emotional and physical abuse.

But prosecutors said the men, who were 18 and 21 at the time of the killings, plotted to off their folks for a $14million – and secured inheritance guilty verdicts in a sensational trial.

The duo has never stopped appealing their case – and their lawyers have asked officials to consider recently unearthed evidence of their father's alleged abuse, including a letter written by Erik to a cousin before the murders.

In October, then-Los Angeles District Attorney George Gascón recommended the brothers be resentenced – potentially making them eligible for parole.

Lyle and Erik's fate is due to be in the hands of a judge at a hearing slated for March 20, which could potentially see them sprung from the slammer.

But new Los Angeles DA Nathan Hochman recently filed a response opposing a petition from the brothers that sought to vacate their convictions or give them a retrial, charging that the felons have a history of "lies, deceit and fabricating stories."