The question is what did BL tell his parents? Obviously, whatever he told them warranted, in their minds, the need to speak to and retain an attorney, even before GP was reported missing and then found.Look at Casey Anthony, she lied about having a job and even walked the authorities inside the building where she used to work. Only then she confessed she wasn't employed.
I can't imagine trying to parent someone who is so adept at lying. I think it's possible Brian completely manipulated his parents and maybe never told them the whole truth at all.