Nick Reiner's "issues were far, far out of his parents' control".

The 32-year-old writer has been charged with first-degree murder in the deaths of his parents - filmmaker Rob Reiner and producer Michele Reiner - earlier this month and insiders say the pair tried for years to help Nick deal with his addiction and mental health issues.

A source told PEOPLE: "They tried so hard already for years.

"At the end of the day, Nick didn't take the help seriously. This was true for years and years. His issues were far, far out of his parents' control.

Nick lied a lot. He was unreliable, but he was also convincing and intelligent. His family was empathetic to [his struggles]. They never lost hope in him, even when he was scaring them or making their lives harder."

Insiders insisted Rob and Michele did everything they could to help Nick.

A source said: "They could never reach stability with Nick. They tried everything - giving him space, keeping him close - but his struggles are so deep. It's just a parent's worst nightmare. They were such lovely people and tried in every way to help their son."

Nick's siblings Jake, 34, and Romy, 28, shared a statement after the murders, detailing the "unimaginable pain we are experiencing every moment of the day."

They said: "Words cannot even begin to describe the unimaginable pain we are experiencing every moment of the day. The horrific and devastating loss of our parents, Rob and Michele Reiner, is something that no one should ever experience. They weren't just our parents; they were our best friends.

"We are grateful for the outpouring of condolences, kindness, and support we have received not only from family and friends but people from all walks of life. We now ask for respect and privacy, for speculation to be tempered with compassion and humanity, and for our parents to be remembered for the incredible lives they lived and the love they gave."