I just keep going back to the suicide idea, but Alan's brother seems to imply he was murdered, so I wonder if he has had the autopsy details to confirm this, or it's just his own hunch?
In my experience, no matter what the facts, family is loath to support a suicide cause of death. That doesn’t mean it wasn’t a murder, just that the brother has been alleging a crime since Alan disappeared. The fact that he’s still alleging a crime doesn’t mean he knows any more than he ever did.