Harry Potter has a twin sister that is sorted into a different House and proceeds to have her own adventures in Hogwarts.

Lyra Black is Bellatrix's daughter, however she disapproves of her mother's allegiance. After growing in an orphanage, where she worked hard to earn money, she becomes the Lady of House Black, is cunning and proud, makes new alliances and unites heirs of other, during the war disgraced Houses.

Severus Snape, being a prodigy, seeks to be the best. After his fourth year he leaves Hogwarts and goes abroad to study under the best Masters of various fields. After hearing about the starting war, Severus starts sending Amelia, a new Auror, healing and various other useful potions, while trying to finish his studies ahead of schedule.