There's often nothing that can be seen by other people. Unless they choose not to see. Is it from other people's point of view, or one of the children's?
I just don't buy the sixteen year old thing, sorry. I'd be asking why they didn't ask for help, or run away, or fight back. I mean, there's only so much you can take. Sure, you might be scared of recriminations but everyone has their limit. If there's no sexual abuse, which is an entirely different ball (sorry) game then it's like 'normal' bullying. You either lie down and die or you fight back.
If the character lies down and dies, story over. If they fight back, then...well, good. You don't want your story to be populated by passive folk, do you?
I dunno...touchy subject for me. I get angry easily; mostly at myself. Go figure.