So now you are saying RFK has access to evidence that the rest of us do not? And he decided not to voice his concerns regarding who was responsible for the death of his own brother? That's a false premise and doesn't add up. RFK may have entertained his own suspicions, but he probably knew less about the evidence in this case than most of us. I'm sure he wasn't measuring the size of Oswald's nostrils etc.
I'm confident that RFK knew things about covert operations and other issues related to the assassination that are still classified. Remember, many of the still classified files are FBI files and as attorney general, Kennedy would've had access to the FBI's secrets. And there are things that the Kennedy family still wants to be kept secret. I'm sure he also spoke to Kennedy's personal physician, George Burkley, who privately told people that there was a conspiracy.
Beyond that, maybe he knew some things about the CIA-Castro stuff and CIA-mafia stuff that has yet to be declassified.
Either way, it's absurd to think that ordinary people like us know more inside information about what was going on in 1963 than people who were in power back then and knew the context of the things we're still learning about...