Scott's little sister could also be super kind - the kind of person who tries to see the good in everyone, even the bad supernatural beings. She might try to rehabilitate a werewolf who has gone rogue instead of just fighting them, believing that there's a chance for redemption.
She might be very intelligent. Maybe she's the one who figures out the weaknesses of the various supernatural creatures they encounter. She spends her time in the library researching and comes up with strategies to keep everyone safe.
One great Scott McCall's little sister fanfiction could be where she discovers her own supernatural powers and has to navigate the same world as Scott, but with her own unique challenges. Maybe she has a different type of werewolf ability or some other hidden power.
Obviously, Scott McCall is one of the main characters. His baby sister is also a central figure. Depending on the fanfiction, characters like Stiles, who is Scott's best friend, could also be important. They might help Scott protect his sister or be involved in her upbringing in some way.
There could be a story where the baby sister is the key to solving a big mystery in the supernatural world. She has a unique connection to an ancient artifact or a prophecy. Scott and his friends initially don't realize her importance, but as the story unfolds, they discover that she holds the answers they've been looking for. This leads to a lot of character development for her and strengthens the bond between her and Scott as they work together.
The people who in the future are his enemies but in the past are just normal people might become his allies. For instance, if there is a character who later turns against him, in the past he might be able to befriend that person and change their future path, so they end up helping him in his time - traveling adventures.
She could be really kind. In contrast to Draco's sometimes haughty attitude, she might be the one who is always helping out the first - years, showing them around Hogwarts and making them feel welcome.
She could be really shy at first. Since Lucy is often quite outgoing in the series, her sister could be the opposite, taking time to warm up to people in the guild. For example, she might hide behind Lucy when meeting new members.
She could be very brave. Growing up in Arthur's shadow, she might feel the need to prove herself just as worthy. So when faced with danger, she doesn't cower but stands up and fights, whether it's against a magical beast or a political enemy.
Her twin sister could be really outgoing. While Hermione is often seen as a bit reserved in social situations, the sister could be the life of the party. She might be more interested in Quidditch than Hermione and be a great flyer. Also, she could be more impulsive. Hermione thinks things through carefully, but the sister could be the type to jump into action without much planning.
He could be really curious. Just like Hermione is always eager to learn new spells and knowledge, he might be constantly exploring the Hogwarts grounds, looking for hidden secrets or new magical creatures.
She could be very strong - willed, much like Naruto. Since she has grown up without her family, she has had to be tough to survive. Maybe she is also very curious about her past and her brother, which drives her to seek out the truth.