Romy Reiner, the daughter of legendary director and actor Rob Reiner and Michele Singer Reiner, reportedly "lived in fear" of her older brother, Nick, prior to him allegedly murdering their parents.

“It feels like Romy has been scared of Nick since she was a child,” an insider with knowledge of the situation told the Daily Mail on Sunday (December 21). “Even before his drug addiction, his outbursts were frightening because they seemed to come out of nowhere. She tried to stay out of his way as much as she could but it wasn’t easy.”

Romy, who will turn 28 on December 27, reportedly "didn't think it was a good idea" for Nick, 32, to be living in their parents' guesthouse prior to their killings last weekend, according to the source.

“She didn’t even like the idea of him living across the street from her,” the insider said of Romy, who lived next door to her parents.

“But she knew they moved him in so they could keep a close eye on him and give him a roof over his head,” the source added.

Romy initially found her father dead inside the home and had her roommate call 911 as she called her father's best friend, actor Billy Crystal, who rushed to the scene with his wife and reportedly saw their friends' bodies, according to previous reports. Romy returned to the scene, at which point paramedics revealed that her mother had also been murdered, an anonymous source close to the family confirmed to the New York Times. Romy didn't see her mother's body at the scene, according to the source.

Rob and Michele Reiner were reported to have been dead for several hours, at which point rigor mortis had already taken place, before their daughter arrived at their home, law enforcement sources confirmed to TMZ. Romy was reported to have suggested that Nick was likely a suspect in their parents' deaths.

Nick was officially charged with two counts of first-degree murder on Tuesday (December 16), with Los Angeles prosecutors requesting the charges be considered under "special circumstances," which can add time to a sentence if convicted, because there were multiple murders. A conviction could result in life in prison without the possibility of parole or the death penalty, though prosecutors haven't yet confirmed publicly whether they'll seek the latter option.

Nick Reiner reportedly stormed off after a tiff with comedian Bill Hader at Conan O'Brien's Christmas Party Saturday night. The 32-year-old is alleged to have interrupted Hader, who told him he was having a private conversation, which resulted in him standing still and staring before "storming off."

The Reiners allegedly got into a "very loud argument" with their son, which led to them leaving O'Brien's party. A source had previously told PEOPLE that Nick Reiner was acting erratically at the party.

“Nick was freaking everyone out, acting crazy, kept asking people if they were famous,” an insider told PEOPLE.

Nick had publicly acknowledged his issues with drug addition and homelessness in the past. Rob and Michele Reiner were reported to also have stab wounds to multiple other parts of their bodies, sources with knowledge of the situation confirmed to the New York Post.

Reiner, the son of producer, writer and actor Carl Reiner and actress and singer Estelle Reiner, initially gained national prominence playing Mike 'Meathead' Stivic on All in the Family and is credit with numerous acting roles during a career that spanned seven decades. The New York City native made his directorial debut with the heavy metal mockumentary This Is Spinal Tap (1984) -- having released a sequel earlier this year -- which was followed up by The Sure Thing (1985), Stand By Me (1986), The Princess Bride (1987), When Harry Met Sally...(1989), Misery (1990) and A Few Good Men (1992).

Ross Kaminsky on the News with Jeana Gondek