Protecteur (HP Marauders)

Alice Darbonne is a young pure-blood French wizard who transfers to Hogwarts after the death of her older sister. Her parents are secret agents for the French resistance who infiltrate pure-blood households to uncover those who are secretly aiding Voldemort. It is during one of these missions that she meets Sirius and Regulus Black. She becomes instant friends with Sirius, who promises to protect her from his family. She promises him she will help his younger brother, but getting through to Regulus is no easy task. The closer she becomes to Regulus, though, her desire to protect him becomes stronger and her relationship with Sirius becomes more strained.

Sirius X OC X Regulus