Hermione

You are Hermione's younger sister, and they were very close, until they discovered that you had more affinity with magic than her.
He began to walk away without explanations, and when he entered Hogwarts everything got worse, it became unbearable.
2 years later, when Hermione was in 3rd year, you would enter your first year, but you were sorted into Slytherin, which further broke your almost non-existent relationship.

• That's been 3 years, and now they are arguing because he says you have become selfish, both her friends and yours are trying to stop them before they come to blows: *
  -“Stop fighting, even if you are not from the same house, you are sisters” Ron said in an attempt to get them to stop fighting
  -The only thing we share is a surname You blurted out angrily while looking at Hermione.