Nicholas Chavez plays Lyle, the elder of the two brothers. Chavez has previously starred in General Hospital (he appeared in 358 episodes!) and is also set to appear in Grotesquerie, premiering this fall.

Cooper Koch plays Erik, the younger brother. Koch has previously appeared in A New York Christmas Wedding, Swallowed, and They/Them.

Spanish actor Javier Bardem—known for films such as Jamón Jamón, Vicky Cristina Barcelona, Skyfall, No Country for Old Men, and many, many more—takes on the role of José Menendez, the murdered father.

Investigative journalist Dominick Dunne reported on the Menendez brothers for Vanity Fair. In Monsters, Nathan Lane (who has starred in everything from The Producers to Only Murders in the Building) plays Dunne.

Ari Graynor takes on the role of the Menendez brothers’ defense attorney Leslie Abramson. Graynor has previously appeared in The Sopranos, Nick & Norah’s Infinite Playlist, I’m Dying Up Here, and Winning Time: The Rise of the Lakers Dynasty.

Psychologist Dr. Jerome Oziel, whom Erik Menendez confided in about the murders, is portrayed by Dallas Roberts. You make recognize Roberts from roles in shows such as The Walking Dead, The Good Wife, or Insatiable.

Jason Butler Harner, who you may perhaps best know for his role as FBI Special Agent Roy Petty in Ozark, takes on the role of Detective Les Zoeller, the primary investigator in the Menendez murders case.

Leslie Grossman takes on the role of Judalon Smyth, Dr. Oziel’s former patient and mistress. Grossman is a regular on Ryan Murphy shows, including various roles on American Horror Story seasons, and starred in Popular, The Good Place, and more.

Craig Cignarelli was one of Lyle’s good friends. In Monsters, he’s played by Charlie Hall, an actor (and Julia Louis Drefyus’s son!) who previously appeared in The Sex Lives of College Girls.

Another Menendez brothers defense attorney, Jill Lansing, is played by Jess Weixler in Monsters. Weixler has previously starred in The Good Wife and The Son.