One possible plot is that the sister was hidden away by Dumbledore for her own protection from Voldemort. But Dumbledore died before he could reveal her location to Harry. Harry then starts to notice some strange behavior among certain magical creatures that seem to be leading him towards his missing sister. As he gets closer to finding her, he also uncovers some long - hidden secrets about his family.
Well, it could be that the sister was kidnapped by dark wizards when she was a baby. Years later, Harry discovers some mysterious clues that lead him to believe she might still be alive. He then embarks on a dangerous journey to find her, facing many magical obstacles along the way.
Maybe the sister was lost in a time - warp accident. In the fanfiction, she could be existing in a different era of the wizarding world. Harry stumbles upon an old prophecy that hints at her existence and her importance in saving the wizarding world from a new, emerging threat. So he has to figure out a way to reach her across time.
Perhaps Bellatrix Lestrange had a secret accomplice who was also interested in the Potter family. After Bellatrix's death, this accomplice decides to hunt down the missing sister to finish what Bellatrix started - destroying the Potter family once and for all.
Well, perhaps she grows up in a different environment than Harry, away from the Dursleys. This different upbringing shapes her character in a unique way. She might have a natural talent for a particular type of magic that Harry doesn't. For example, she could be really good at divination and use her skills to foresee the coming dangers to Harry and the wizarding world. And she would be constantly trying to keep her identity as Harry's sister a secret from the wrong people while still trying to support him in his fight against evil.
In a 'Harry Potter and His Little Sister' fanfiction, the sister could be a new student at Hogwarts when Harry is in his later years. She struggles to fit in because of being Harry Potter's sister. Harry has to help her deal with the pressure, make friends, and also face the threat of a new dark wizard who has a vendetta against the Potter family.
One possible plot could be that Lemon discovers she has a special magical ability that is different from Harry's. For example, she might be able to communicate with magical creatures in a unique way. Harry then has to protect her from those who might want to use her ability for bad purposes.
One possible plot could be that a dark wizard kidnaps Harry Potter in order to steal his powers. In the chaos of the abduction, Harry loses his glasses. Without his glasses, he has trouble seeing clearly which adds to his vulnerability. The wizard might be working for Voldemort or could be a new enemy. His friends Hermione and Ron would then embark on a quest to rescue him. They would face many challenges along the way, like getting past dark magic traps and finding the location where Harry is being held captive.
The plot might revolve around the older sister being a part of a prophecy too. Just like Harry, she has a special destiny. But instead of being in the spotlight like Harry, she works behind the scenes to ensure Harry's success in the fight against Voldemort. She could be the one who finds out about Horcruxes first and guides Harry in that direction, all while dealing with her own challenges at Hogwarts, like trying to keep her identity as Harry's sister a secret from the wrong people.
One possibility is that Harry discovers a long - lost sister and takes on the role of a protector. He might teach her magic in secret, away from the prying eyes of the wizarding world authorities. Maybe they live in a hidden cottage and he passes on the skills he learned at Hogwarts to her.
The sister might have her own group of friends in the wizarding world. When she takes in Harry, she brings him into this circle. They all contribute to his upbringing. For example, one friend could be a potions expert and teach Harry about potions in a fun way. Another could be a great dueler and train Harry in combat magic. His sister coordinates all this, ensuring Harry gets a well - rounded magical education and a loving family environment.
Well, one possible plot is that the younger sister is a target of the dark forces because of her relation to Harry. She has to constantly prove herself and fight against the stigma. She could form a secret club within Hogwarts to train students in self - defense against the dark arts in a more creative way than what Umbridge allowed. And she might also have a magical pet that is not common, like a miniature phoenix.
One possible plot could be that Harry discovers her relation to Sam and Dean early on. She then tries to balance her wizarding education at Hogwarts with the hunting life of her brothers. Maybe she uses her magic to fight off the same demons that Sam and Dean are hunting, but in a different, more magical way.