If they author turns this in to a romance between them ill genuinely get mad.. like... they are super protective of her, yes, as they should.
They all should come with terms that, yes, when they were young they did stupid stuff because they tought she was a replacement. And that guilty of stupid mistakes, because they were kids, made them over protective of her and made them want to compensate for what they did, on top of the trauma made by that stupid aunt.
I don't want her to be in a romantic relationship with any of them.
I want them to acknowledge that yes they had issues and now they are indeed a family.