The siblings' brother Nick Reiner, 32, is suspected of murdering their parents.
"The terrible and devastating loss of our parents, Rob and Michele Reiner, is something no one should ever have to experience," they wrote in a statement.
"They weren't just our parents; they were our best friends. We are grateful for the condolences, kindness and support we have received, not only from family and friends but from the public."
The siblings ask people to show "respect and integrity" and handle speculation with "compassion and humanity." They conclude by saying they want their parents to be remembered for the "incredible lives they lived and the love" they gave.
