From a family whose blood was so pure they'd been included in the Sacred 28, Julius Selwyn had no reason or intention to sink to even looking at a muggleborn witch, and for 25 years of his life he didn't. Until, that was, he met the Japanese witch Hakumo Kagome.
Their relationship was unexpected, to say the least, but with Julius capable of causing serious damage to the family name his parents made the decision to refrain from disinheriting him with two conditions: Hakumo had to pretend to be pure-blooded, and she had to sign a prenuptial agreement. Both agreed to this, though Hakumo was a little concerned in regards to the prenup, and they were married a few months later, when she became pregnant.
10 years and seven children later, Aline Giselle Selwyn made her way into the world. Her first few years were uneventful, but shortly after her fifth birthday, Julius got home early from his high-up ministry job to find his wife in bed with a man he'd never even met. The divorce was filed as soon as he could get it.
The prenuptial agreement saved the Selwyns' family fortune, but there was no such barrier to save Hakumo's reputation. The only thing that stopped her ex-husband from declaring her real blood status was his love of their children. Oh, and his regard for his family reputation.
Aline's first sign of magic occurred when she was six years old and began chatting away to a grass snake in the garden, observed by a bemused older brother. Like almost every one of her older siblings, Aline was always a precocious child, but with this new revelation her father started putting even more pressure on her to be great.
Always eager to please, Aline tried her very best until she began Hogwarts. But then, after beginning contact with her mother (against her father's wishes), she gradually lost interest until she was only putting in enough effort to scrape a pass. She stopped doing homework almost completely, and became a veteran of all-nighters whenever she couldn't skip an assignment. Whenever one of her extremely successful older siblings, her father or one of her professors tried to push her towards "fulfilling her potential", the more she completely and utterly refused.
Now in her fourth year, the majority of her classmates have come to the conclusion that the sorting hat made a serious mistake in sorting Aline into Ravenclaw. Even she seems to believe it.