I understand there's a curiosity about Sam's family and how much they knew about Sam's drug dealing, which I have to add, is pure speculation on our part. Is it fact that Sam's parents lived at those premises during that period, if at all?
RB and AD's parents won't be under the same level of judgment and scrutiny as Sam's parents, and rightfully so.
IMO, these discussions keep getting sidelined regarding RB and AD because of questionable personal anecdotes which describe these characters as, peace loving and hard done by individuals who are victims of circumstance. Even from the little we know, this isn't the case.
RB and AD discarded Sam's body and carried on like normal hoping to escape justice. They have little regard for human life and the suffering that Sam's family endured not knowing if he was alive or dead. RB and AD should be under the microscope and they will be once it goes to trial and the tales they tell. imo