The poster you responded to suggested that BL's estate be sued, not his parents. It would be an action to gain information through depositions, but it would be painful for both families. I do not think BL has an estate that would cause any normal lawyer to take such a case on contingency - they'd have to want to do it to help Gabby's family. Would a judge rule that the Laundrie parents could be deposed in such a case? I have no idea - but I'm thinking that wouldn't really work. The people who would need to be deposed would be SAR personnel in Wyoming, LE, coroner, etc.
Not sure at all what Gabby's family would gain from that, that they don't already have access to. Brian's full coroner report, I guess, if for some reason that is withheld.