I adore this story. Why? Because the entire family is nice. The father is nice. The brothers are nice. The sister is nice. The stepmother is nice. Normally, one of these would be hostile and actually try to bully the new child that came from another mother. There would even be political reasons for hostility because she might actually be a threat to one of her siblings' position for the throne or something.
But no, they are ALL nice people and they ALL want to take care of her, love her, and be a family for her.
This is the type of story I wanted to see more often.