Prosecutors said Erik and Lyle Menendez should be resentenced for the 1989 killings of their parents in the family's Beverly Hills home.
Los Angeles County District Attorney George Gascón announced that his office would recommend the brothers receive a new sentence of 50 years to life.
But because they were under 26 years old at the time of the crimes, they would be eligible for parole immediately, he said, giving them a chance of freedom.
Resentencing must now be approved by a judge, with a hearing due in the next month.
The Menendez brothers were sentenced in 1996 to life in prison without the possibility of parole.
Lyle Menendez, then 21, and Erik Menendez, then 18, admitted they fatally shot their entertainment executive father, Jose Menendez, and their mother, Kitty Menendez.
The brothers said they feared their parents were about to kill them to stop people from finding out that Jose Menendez had sexually abused Erik Menendez for years.
The brothers' extended family has pleaded for their release, saying they deserve to be free after decades behind bars.
Anamaria Baralt, a niece of Jose Menendez, said the district attorney's "brave and necessary" decision means "Lyle and Erik can finally begin to heal from the trauma of their past."
But not all of the family support resentencing, with lawyers for Milton Andersen, the 90-year-old brother of Kitty Menendez, filing a legal brief asking the court to keep the brothers' original punishment.
"They shot their mother, Kitty, reloading to ensure her death," Ms Andersen's attorneys said in a statement Thursday.
"The evidence remains overwhelmingly clear: the jury's verdict was just, and the punishment fits the heinous crime."
Mr Gascón said he made the final decision only an hour before the news conference and that family members were told just minutes before.
Though Kitty Menendez was not accused of abusing her sons, she facilitated the abuse, her sons' legal filings allege.
The Menendez brothers were tried twice for their parents' murders, with the first trial ending in a hung jury.
Prosecutors at the time contended that there was no evidence of molestation, and many details in the story of sexual abuse were not permitted in the second trial.
Prosecutors also claimed then that the brothers were after their parents' multimillion-dollar estate.
The Menendez case has gained new traction in recent weeks after Netflix began streaming the true-crime drama " Monsters: The Lyle and Erik Menendez Story."
