Rob Reiner’s closest friends are stepping up to support the director’s children following his and his wife’s shocking murders on Sunday.

“Rob and Michele were beloved in Hollywood and their friends like Billy Crystal and Albert Brooks are truly like family and fiercely protective,” an insider told People on Thursday.

The “Stand by Me” filmmaker and his wife of 36 years, Michele Singer Reiner, shared three children: Jake, 34, Nick, 32, and Romy, 28. Rob also had another daughter, Tracy, 61, whom he adopted during his first marriage to Penny Marshall.

Nick was arrested just hours after his younger sister reportedly found Rob, 78, and Michele, 70, stabbed to death in their Brentwood, Calif., home on Dec. 14

He has since been charged with two counts of first-degree murder in connection with the death of his parents, and his arraignment is currently scheduled for Jan. 7.

“They are being incredibly strong and have a huge support system they can lean on,” the source said of Jake and Romy, adding that the two “will never be alone as they try to face this.”

“It’s of course been a huge shock to the system,” the insider continued. “This nightmare came out of nowhere for them, but they’ve been surrounded with support since the second they found out.”

Jake and Romy, for their part, expressed gratitude for the strength and support they’ve received in the wake of their parents’ tragic deaths in an emotional message shared on Wednesday.

“Words cannot even begin to describe the unimaginable pain we are experiencing every moment of the day,” the pair told Page Six 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,” Jake and Romy continued. “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.”

The siblings, however, made no mention of their brother Nick and his suspected role in the Reiner family tragedy.

“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,” the late “Princess Bride” director’s two kids concluded.

Crystal and Brooks, as well as a handful of the slain couple’s other famous friends, remembered Rob and Michele in a touching joint statement of their own on Tuesday.

“Rob was also a passionate, brave citizen, who not only cared for this country he loved, he did everything he could to make it better and with his loving wife Michele, he had the perfect partner,” the group, which also included Larry David and Martin Short, wrote.

“Strong and determined, Michele and Rob Reiner devoted a great deal of their lives for the betterment of our fellow citizens,” they continued. “They were a special force together — dynamic, unselfish and inspiring.”

“We were their friends,” the grieving group concluded, “and we will miss them forever.”