You're still my bestie

Harry and Ilia Potter are twins-- Living with their Aunt Petunia and Uncle Vernon. They were best friends, having to deal with everything their only relatives together. When they learned that they were both wizards, they enter the world of a new school and a new world.
Once they get to school though, something splits them apart. They soon hate each other, having each other at their necks.
Can the siblings ever be friends again?