In truth, I believe Qabil would prefer to use her instead of her brother, given that Cabal no longer has the time to see her with child and to raise that child to be less flawed than Ghalib. I believe Anaf, specifically, was to have charge of that child's upbringing--he was to come to Fallenheart with Faris if Qabil decided it was time to cut the Cabal's losses with Ghalib. They did not anticipate the Nation-eaters returning.