Going by the cover if her "brother" is actually a love interest I'll be kinda sad. Mostly cuz of the whole they were family for 13 years things But that won't stop me from reading.
well after they meet the real daughter, both of her parents and brother kicked her out of family and give her a pocket money.
Her real family still cold towards her because they love the previous( blonde girl)daughter.
she marry his fiancee, later they build a railway company together with the help of her former brother
no wincest, she marries her original Finance at 18 and the end of the novel. It seemed he was truly taken with her and did not want to break the engagement when she got "demoted" in the side chapter for him finding out about the cancelation
She really does seem like a heroine, nothing special, just kinda main character vibes, like a “Everything is going to go my way in the end, so it’s fine” kinda vibe