People can be held responsible for statements made by their lawyer: Amber Heard "won" $2,000,000 for a statement made by Johnny Depp's lawyer.
On the other hand, this case is quite different. Bertolino made no accusations against GP or her parents. Any knowledge of the case he possessed would have been told to him by BL or his parents, and this is protected by attorney-client privilege. SB has stated that, at the time, he represented all three Laundries. If BL provided his lawyer with false information leading to the public statement, can his parents be held liable?
BL's "confession" is complete bull****. Based on this bizarre tale, I have no reason to believe he was brutally honest with his parents or his lawyer. I know many posters here believe he told his parents all the details of his crime, but that just seems too out of character for the person who claimed to have help put her out of her misery.
In this case, I suspect only two people knew what really went down out west, and both of them are dead. I suspect that when this lawsuit is over, there will still be divisions among us as to the L's actions and motives.