District Attorney Nathan Hochman told reporters outside a downtown Los Angeles courthouse that prosecutors took into account the wishes of the surviving Reiner family members in reaching their decision.
The announcement came shortly before Nick Reiner, 33, was scheduled to appear for a pre-trial hearing where the judge is expected to set a preliminary trial date and consider various pleadings in the case.
Rob Reiner, 78, and his wife, photographer Michele Reiner, 70, were found stabbed to death in their home in Los Angeles' Brentwood neighbourhood last December in one of the most shocking celebrity homicide cases in Los Angeles history.
Nick Reiner, the younger of their two sons, was arrested later that day and charged with first-degree murder.
The maximum penalty prosecutors said they would now seek against him is life in prison without parole.
A grand jury indicted Nick Reiner in August, allowing prosecutors to go to trial without a preliminary hearing.
He has acknowledged a years-long struggle with substance abuse and mental health issues.
Rob Reiner gained fame as a co-star in the 1970s hit television comedy All in the Family and later directed popular films including When Harry Met Sally, This Is Spinal Tap and The Princess Bride.
