Ekho Sprout

Backstory

Some info: This character exists during the marauder's era and their story is intertwined with theirs but I won't go into full detail. 

Their mother (Psyche Burke) was a powerful witch in the Burke family of the sacred 28. She was disgraced for secretly marrying a muggle, Fynn Sprout. They had one child who they named Ekho Sprout. However, by the time she was 6, both their parent died in a terrible accident. Ekho's grandmother (Nozéa Burke) hesitantly took her in and covered up her half-blood status. Because their great-grandmother was a Black by blood, Ekho spent a lot of their time over at their house and became good friends with Sirius and Regulus. However, Nozéa was not a kind woman and restricted much of what Ekho could do. She also held their blood status over her head and would often use it as an excuse to be terrible. 

Both Ekho and Sirius could relate to this and would often act out and cause mischief when together. One time they took it a little too far and Walburga flipped out forbidding us to visit anymore or associate with Sirius as I was a "bad influence" on him. 

Now it is Ekho's first year at Hogwarts and to her disappointment, he is sorted into Slytherin. Now they have no idea whether or not Sirius will still be friends with them or if he'll be mean.