Eric And Lyle Menendez are currently awaiting word from the LA District Attorney George Gascon for an important case update … but her fellow inmates are already acting like they're getting out, TMZ has learned.

A source at the Richard J. Donovan Correctional Facility tells TMZ that prisoners are already lining up and attacking the Menendez brothers' mansion inside… all in the hopes of snagging a famous souvenir or two.

We're told that everything from clothes to their televisions is up for grabs at the moment, even though it's forbidden in prison.

That's what our source says technically The siblings aren't supposed to reveal anything… but that doesn't stop the inmates from forming an under-the-radar line at the San Diego facility.

Despite all the new attention given to the Erik and Lyle case, we're told the brothers have been unusually quiet and reserved this week. It's obvious they were “nervous” about what will come from the DA's office, our source claims…since their fate rests in Gascón's hands.

That said… the infamous duo have promised their fellow inmate friends that they will do what they can on the outside to help their cases!

Gascon held a press conference In early October, he confirmed that his office was reviewing new evidence in the case … which could lead to a resentencing or new trial, potentially leading to the two being released after spending nearly 35 years behind bars.

Erik and Lyle are currently serving life sentences without parole for killing their parents Jose And Kitty Menendez in 1989. The infamous brothers were tried twice for the murders… their first trial ended in a mistrial due to the jury's deadlock.

Erik and Lyle's allegations of sexual abuse against their late father were not allowed to be brought forward at their second murder trial… where they were ultimately convicted.