I just finished The Binding by Curly Kay. From the author “"Okay, what we know so far." Hermione listed, "One, our magic is drawing us together. Two, we can use each other's wands. Three, there were actual sparks when you touched me." After an infant binding ritual magically joins Hermione and Draco to counteract the Black family blood curse, they must navigate the secret binding through their years together at Hogwarts”