Later on Tuesday, the 32-year-old will be charged with two murders and for using a dangerous weapon, a knife, prosecutors announced.
If convicted on all counts, Reiner faces life in prison or the death penalty. Prosecutors have not yet decided whether to seek the death penalty.
The death penalty can be imposed in California, but it has not been applied in almost 20 years.
Nick Reiner has hired high-profile lawyer Alan Jackson, who has defended film mogul Harvey Weinstein and actor Kevin Spacey, among others.
Reiner was supposed to appear in court earlier on Tuesday, but Jackson said he could not be brought to court until Wednesday at the earliest due to health reasons.
It was Sunday when Rob Reiner and his wife Michele Singer Reiner were found dead in their home in the Brentwood neighborhood of Los Angeles.
According to police, the couple was found in their bedroom.
There were no signs of a break-in, sources told The Los Angeles Times.
