So this daughter of his was a prisoner for 24 years, had SEVEN children down there and no one knew? The ones kept in the basement never tried to escape? My god, this is beyond understanding. The daughter wasn't an infant when he locked her up for god's sake.
The daughter must have been simple-minded.
From reports over here, she was not simple minded. God knows how long he kept her drugged and tied up though - that's how he got her down there in the first place. Once she had children, he might have threatened them to keep her quiet. As for the kids, it was the only world they ever knew, and he was the owner of that world. Escaping? - sound-proofed solid concrete walls and floors, a door that had an electric keypad lock on it, and rules against anyone going in the cellar itself, let alone near the door. I mean, this was an apartment building, not the basement of a house, and the guy who did it was the caretaker/owner? of the building.
And we don't know if or how many times she did try to escape. Normal women can be caught in highly abusive situations and feel like they can't escape, especially when they can't actually escape. Who knows what he threatened her with, or what sort of things he did to break her. If she was 11 when the abuse started, as she says, she was probably already broken when he locked her up.