One possible plotline could be that Mal has been away on some sort of adventure or mission and her sister has been left behind. The fanfiction could be about the sister's longing for Mal during her absence and how she copes with the situation. Maybe she discovers things about herself in the process.
Perhaps Mal has had a falling out with her sister and they've been separated. The story could revolve around how both of them are missing each other but are too stubborn or hurt to reach out at first. Then, through a series of events, they start to bridge the gap between them. This could involve other characters from their world helping or hindering the process.
One possible plotline could be Mal discovering her true identity as Aurora's daughter and having to deal with the new - found knowledge. She might struggle with fitting into the world she thought she knew or face challenges from those who oppose her new status.
You can try looking on fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfictions, and you can search for 'Mal Sister I Miss You' in the search bar. There are often tags and filters to help you narrow down the results to find the ones that suit your taste.
Maybe there's a prophecy that says something bad will happen to one of them if they stay friends. But Mal and Evie don't care about the prophecy. They fight against the forces that try to keep them apart, whether it's a magical curse or a group of people who oppose their friendship. Their loyalty to each other is unwavering.
A plotline might involve them facing a great danger together as a married couple. They could be in a magical or non - magical world where they have to use their combined skills and love for each other to overcome threats. For example, they might have to fight against an evil force that is trying to tear them apart or destroy their world. Their relationship would be tested and strengthened through these challenges.
One possible plotline could be that Tatia's sister is a long - lost relative who suddenly shows up in Mystic Falls. She might have some hidden powers or knowledge about the vampire - werewolf - witch triangle that the main characters are unaware of, and this knowledge could either help or hinder them in their battles.
Maybe the sister is a hidden Jedi. She and Rey meet by chance and then they team up to find an ancient Jedi artifact that could save the galaxy from a new threat. They face off against various enemies, including some Sith cultists.
The sister could have her own love story intertwined with the events of the wizarding world. She might fall in love with a Gryffindor, which would be a huge scandal in the eyes of some. This relationship could be a source of tension, not only within her family but also in the wider wizarding community. And as Severus tries to protect his sister from the dangers of the wizarding war, her relationship could add an extra layer of complexity to his already difficult situation.
Perhaps she has a special connection to an ancient and powerful ninja art. This could lead to her being targeted by some villains who want to use her for their own gain. Naruto then has to step up to protect his sister, and in the process, they both learn more about their family's past and their own powers.
Another plotline could be that she was cursed as a child and lost her memories. Years later, she starts to regain her memories and realizes she is a Malfoy. Draco then has to help her navigate the wizarding world that she has forgotten while also dealing with his own feelings about having a long lost sister. It could involve adventures in finding a way to break the curse completely.
One possible plotline could be that Naruto's sister secretly helps him during his difficult times in the village. Maybe she provides him with extra training resources or helps him outwit the bullies without him knowing it's her at first.