Bara no Tame ni (1992)

Yuri is short, chubby, and not particularly pretty. And on the day she was dumped by her boyfriend (because he found a prettier girlfriend), she goes home to find that her grandma, her one and only relation, had a stroke and is at death’s door. After her grandmother’s death, Yuri finds a letter from her grandma that tells her she has FAMILY in Hokkaido. And to her surprise, her mother is the famous actress, Shoko Hanai. Yuri goes to live with her newfound family, which includes an older sister and brother, and a younger brother, all with different fathers. But to her chagrin, she discovers that she is an ugly duckling among beautiful swans. And now she’s falling in love with her older brother, Sumire, and her rival is her younger brother, Aoi...

Source: www.anisearch.com/manga/3382