If you were born before 1980, you probably know all about Lyle and Eric Menendez — the brothers arrested and charged in 1990 with the murder of their parents, Jose and Mary “Kitty” Menendez. The same, it seems, may also be true if you’re a member of Gen Z.

The Menendez brothers, who were sentenced in 1996 to life in prison, have become the subjects of hundreds of fan accounts across social media, most visibly on TikTok and Instagram. Many of them are run by people born years after the case closed who, in learning its details, have become some of the brothers’ most vocal defenders.

Their arguments reflect debates that played out during the brothers’ 1993 trial, which was among the first high-profile cases to be broadcast on Court TV and helped fuel the modern era of true crime. The prosecution claimed the brothers were motivated by their inheritance — a theory bolstered by their Beverly Hills upbringing and a lavish spending spree in the months before their arrest — while the defense argued that they were victims of sexual abuse.

“When I saw a clip of Erik testifying about the molestation by his father, I was shocked to say the least,” Jordan Whynn, 24, a paramedic science student in London, wrote in an email. As he learned more about the case, he became “disgusted with the way the media at the time and in subsequent years downplayed the brothers’ abuse.” He cited Alan Dershowitz’s 1994 book “The Abuse Excuse,” in which the lawyer argued that accused criminals like the Menendez brothers use claims of abuse to avoid punishment.

After watching the entire trial during lockdown — it’s on YouTube — Mr. Whynn came to the conclusion that “the brothers had an unreasonable but genuine belief that their lives were in danger” when they shot their parents. He decided to set up an Instagram account called @MenendezSupporters to post about the brothers’ case.

Robert Rand, who covered the Menendez trial as a reporter and has since become an advocate for their cause, traces the latest wave of interest in the case to the 2017 release of “The Menendez Murders: Erik Tells All,” a true crime docu-series on A&E that featured in-depth interviews with Erik Menendez about his claims of abuse. (It began streaming on Hulu in 2019.)

Toward the end of 2020, Mr. Rand noticed an increase in traffic to his website, MenendezMurders.com. “We typically have 500 visitors a day,” he wrote in an email in late January. “Last weekend, we had 50,000 visitors.” Google Trends shows searches for the term “Menendez brothers” spiking in mid-December.

On Dec. 23, Fabienne Bersching, 20, who works in retail sales in a small town near Wiesbaden, Germany, was scrolling through TikTok when she came across footage from the brothers’ trial. “I just thought, ‘Well, that’s not something you see every day on TikTok,’” she said.

She soon found more accounts posting Menendez content and watched the A&E documentary with her mother; it left her with a strong feeling that the brothers had been wrongly convicted. On Jan. 1, Ms. Bersching started an Instagram account of her own, where she connected with supporters across the world.

“Of course, there are people from America, but I also met people from Hungary, and from France,” she said. Many, she said, are as young as 15. Their shared goal: “Get them out of prison,” Ms. Bersching said. “31 years are enough.”

How does her mother feel about her newfound cause? “My mom is a person that says like, ‘You know, they killed their parents, and that’s wrong,’” she said. “I’m always like, ‘Yeah, it is wrong.’ I’m not supporting the fact that they killed their parents, and I never will. But it’s the background story that’s so much more important to me.”

Sharon Ross, a professor of media studies at Columbia College Chicago who studies television and fan behavior, wrote in an email that the boom in true crime, alongside “short-form social media like TikTok that encourages ‘bite-sized’ high-impact posts that aim to generate reactions,” has fueled debate among young people online on “big picture issues such as how we define truth, justice, and equity.”

Such discussions defy the black-and-white morality tales spun as entertainment in the ’90s. “The 1990s in the U.S. was the decade for infotainment, from more normative news coverage to Jerry Springer,” Ms. Ross wrote, citing the headline-dominating stories of O.J. Simpson, Nancy Kerrigan and Lorena Bobbitt.

The Menendez brothers belong to a category of criminals whose stories are being retold with more nuance and reassessed in light of shifting public opinion. “We are right now much more attuned as a society to the realities of the impact of domestic violence, sexual abuse and harassment, and racist violence and harassment,” wrote Ms. Ross. “This allows us to look at ‘reactions’ to such elements with 20/20 hindsight.”

Aileen Wuornos, a serial killer who was executed in 2002 for the murders of seven men in Florida between 1989 and 1990, said the killings were self-defense against sexual assault; she has since come to be seen as a misunderstood feminist figure. (There are plenty of TikTok videos about her, too.) Same goes for Ms. Bobbit, who cut off her husband’s penis in 1993 after he raped her, she said.

In addition to inspiring sympathy from young people learning about their case, the Menendez brothers have been cast by some on social media as stars (their video edits invoke hallmarks of “stan” culture, like upbeat pop music and dreamy soft-focus shots) and sex symbols. This isn’t new: When they were first arrested, the brothers received 1,000 letters a week at the Los Angeles County jail, Mr. Rand said, some of which contained nude photos. He remembers seeing “groupies” lined up overnight to get seats at their trial.

But some posters see such romanticization as a distraction from their advocacy. “I want people to stop sexualizing them and actually focus on the case, because their looks have nothing to do with it,” said Zoe Patterson, 17, an avid Menendez supporter from Melbourne, Australia, who made fan accounts on Instagram and TikTok in August. She hopes the brothers never encounter “those sexualization edits, considering they’re both married and have suffered a traumatic childhood.”

“I just want to thank them for inspiring me — not only me, but other supporters as well,” she said, citing reports of the brothers’ efforts running therapy groups for other inmates. “I think what they’re doing is absolutely amazing.”