Exactly. The bit with Zarabeth is perfectly clear. She's being bitterly wry when she comments that her only crime was "choosing" her kinsmen unwisely. She didn't choose them at all or commit any crime herself. She just had the bad luck to belong to a family that was purged by a sadistic dictator. We can speculate as to exactly why he didn't just have her killed, but it seems it would have been bad public relations for some reason. Maybe she was popular with the masses? Or had influential friends at court?
In any event, a entire family being punished for the crimes of a few members is hardly unprecedented, particularly if there was some sort of attempted coup or assassination involved. Zor Khan may have wanted to avoid the assassin's relatives seeking revenge--or becoming a rallying point for other rebels or dissidents.
(Remember how Corazon Aquino became a symbol of resistance in the Philippines after Marcos allegedly had her husband killed?)