When she was 1st rescued from here we only heard of her dad really. She mentioned he tried to help her. She might have also said something like “my mom was busy with my siblings” then but I only remember them mentioning her dad with a small look and they didn’t even really show her mom’s face with any detail when she left with him. Cause she was living in isolation at the time. But yeah, I don’t think they are super important. I think this is in part a closing arc for her with loose ties from her family. And her siblings are younger than her so I don’t foresee them playing a big antagonistic arc. Just part of this arc is the family she left behind.

I don’t know who this Kazane guy thinks he is, but he needs a foot up his ass. Also, who are these “other children” in Nanao’s family? Are they her siblings or step-siblings?