The couple's son, Nick Reiner, has been charged with the murder of the Princess Bride director and his wife and following the tragedy on Sunday, their other two kids have broken their silence about the "horrific and devastating loss".
"Words cannot even begin to describe the unimaginable pain we are experiencing every moment of the day," Romy, 27, and Jake, 34, said in a statement.
"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."
The siblings went on to thank people for their love and support and appealed for "compassion and humanity" when discussing the circumstances surrounding their deaths.
"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," they said.
"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."
Their statement was released as their brother made his first court appearance on Wednesday after being charged with two counts of first-degree murder.
The 32 year old - who has battled addiction and homelessness over the years - wore a blue anti-suicide smock and shackles during his appearance at Los Angeles Superior Court.
Alan Jackson, his lawyer, declined to enter a plea for his client.
Nick's arraignment has been scheduled for January 7.
Romy, along with a friend, discovered the bodies of her parents in their bedroom after being alerted when Rob and Michele did not answer to a scheduled visitor on the security buzzer of their home.
A call to emergency services brought police and medical assistance to the address but the couple were already dead.
Romy also called family friends Billy and Janice Crystal, who arrived quickly to the scene from their home nearby.
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