Davis, 72, had won three recommendations for release from the California parole board every time he appeared before the panel since 2010, but all three decisions were later reversed by California governors.
In spite of the reversals, Davis' past successes in winning a parole recommendation have prompted a representative for murder victim Gary Hinman's family to attend Thursday's parole hearing.
Debra Tate, whose sister Sharon Tate was a murder victim by Manson followers, said she will oppose any parole for Davis.
"On Thursday morning, it is our job to remind the parole commissioners exactly how heinous the two crimes that Bruce Davis committed were," said Debra Tate, a representative for Hinman's family. "It is my very firm belief that this man continues to pose a grave threat to society."
Davis was sent to state prison on April 21, 1972, for the first-degree murders of Hinman, a musician, and stuntman Donald "Shorty" Shea in 1969.
In 2010, 2012 and 2014, the parole board granted Davis parole.
In the second case, the board explained it made such a recommendation because of Davis' "positive adjustment, record of no recent disciplinary problems, and for successfully completing academic and vocational education and self-help programs."
But current Gov. Jerry Brown reversed the 2012 and 2014 decisions, said Luis Patino, a spokesman for the California Department of Corrections. Then-Gov. Arnold Schwarzenegger reversed the 2010 recommendation, Patino said.
If Davis is successful this time, he would become the first Manson "family" member to be freed solely for good behavior.
Thursday's hearing will be held at the California Men's Colony,
where Davis is imprisoned, in San Luis Obispo, Patino said.
The Manson group's gruesome killings inspired the best-selling book "Helter Skelter" and made their ringleader Manson a cult figure.
The 1969 rampage killed several people, including 8-months-pregnant actress Sharon Tate.
Manson is serving a life sentence for his role in nine murders. He was denied parole for the 12th time in 2012
. His next such hearing is set for 2027, when he would be age 92.