Brinkley said Kennedy's wife, Ethel, made a deal after his assassination in Los Angeles in 1968 that allows her to maintain control of the papers. And she has not decided to release him.
"Mrs. Kennedy is not doing anything wrong they are really her papers at this point," Brinkley said Monday on "CBS This Morning."
Brinkley said the papers are personal in nature and are likely to include correspondence between Kennedy and his family members and friends. However, he said the papers also are likely to include information on the Cuban Missile Crisis and other key policies he was involved in as attorney general.
"The Kennedy family says they're going to be opened, it's just a matter of timing," Brinkley said.
Brinkley also said the family vacation home in Hyannis Port, Massachusetts is the cause of a Kennedy family disagreement about what to do with the estate.
"The good news is... the house is saved," Brinkley said because the late Senator Ted Kennedy's wife, Vicki, donated the house to preserve it.
The presidential historian also said that since Senator Kennedy died, the Kennedy family has been void of a central patriarch in the family.
"All the Kennedy family would galvanize around him. That doesn't exist anymore," he said.