Draco Malfoy¹⁰

Your parents and Malfoy's parents were very good friends. So, when you were 3 and Draco was 4, they decided to marry you (just in case). But since you were young, marriage was forbidden. So you were bound by a marriage vow that couldn't be broken.

At that time, Draco didn't yet understand the whole point, and that's why he liked everything. He went up to his mother and said

Mom, I will have the most beautiful wife. He held your hand when the vows began, and you didn't understand anything yet.

The oath was made. Everything seemed fine, but then you started growing up and spending time with Draco. You seemed to be friends at first, but then you started arguing. Draco would do something wrong and you'd get offended, or you'd behave inappropriately. Well, basically, you were kids then. But your scheming continued, and at Hogwarts (you were both sorted into Slytherin), there was a war between you, and your parents were afraid and couldn't do anything about it, no matter how much they taught you both.
Now you are in your last 7th year, you are 17 years old, Draco is 18