Maybe Sesshomaru discovers that Inuyasha holds the key to some great power and decides to raise him in order to use that power for his own gain, but along the way he actually starts to care for Inuyasha like a real brother. He could teach Inuyasha about their demon heritage and the ways of the samurai, which would be a great character development for Inuyasha.
One plot idea could be that Sesshomaru has to raise Inuyasha in a world where all the other demons are against them being together. He has to teach Inuyasha how to control his powers while also protecting him from various threats.
One idea could be a story where a powerful magic affects both Sesshomaru and Inuyasha, causing them to be in a situation where they have to deal with the unexpected pregnancies. This could lead to them having to put aside their differences and work together to understand what's happening to them. Maybe they go on a journey to find a cure or a way to handle the situation, all while facing various challenges from other demons who see their condition as a sign of weakness.
One idea could be that they get transported to a magical realm where they have to solve a series of puzzles to return home. Along the way, they learn more about each other's strengths and weaknesses. For instance, Inuyasha's impulsiveness might get them into trouble at times, while Sesshomaru's calmness helps them get out of it.
Another fanfiction concept could be set in an alternate universe where they are all students in a school. Inuyasha might be the troublemaker, Kagome the studious one, and Sesshomaru the aloof and brilliant student. There could be a mystery at the school that they have to solve together, and through this, they form an unlikely friendship.
In fanfiction, the baby could be the key to unlocking some long - lost secrets in the Inuyasha universe. Since Sesshomaru and Inuyasha have such complex histories and lineages, the baby might hold the answers to ancient prophecies. It could also have a special bond with the Jewel of Four Souls, perhaps having a unique way of controlling or protecting it that neither of its parents had. And of course, there would be all kinds of emotional drama as the two brothers - turned - co - parents deal with their new relationship.
One plot idea could be that their little sister has a unique power that both Inuyasha and Sesshomaru don't fully understand. This power could attract various demons who either want to use it or destroy it. Another idea is that she gets lost in a different realm and has to find her way back while learning about her own abilities and the relationship between her brothers.
Perhaps Kikyo is in trouble and Sesshomaru is the only one who can save her. But in the process, he discovers a side of her that he didn't expect, like her strong will and determination even in the face of death. This could lead to a newfound respect between them and the start of an unexpected friendship or more.
One idea could be that Sesshomaru and Sango are forced to team up to fight a common enemy stronger than they've ever faced before. During their journey together, they gradually learn to respect each other's skills. For example, Sango's expertise with her weapon, the Hiraikotsu, impresses Sesshomaru. Another plot could involve Sesshomaru getting injured and Sango taking care of him in a hidden forest. This situation would make Sesshomaru see Sango in a different light and start to develop a friendship that could potentially turn into more. A third idea is that they both get transported to a strange, magical realm and have to rely on each other to find their way back home while also uncovering the secrets of the new world.
One interesting storyline could be about a young Inuyasha and Sesshomaru being forced to work together due to a common threat to their family. They might start off hating each other as they usually do, but as they face challenges, they gradually learn to respect each other's abilities.
One idea could be Minato teaching Naruto how to master the Rasengan at a very young age. Since Minato was the creator of it, he could pass on his in - depth knowledge. Another plot could be Minato protecting Naruto from the early threats that Naruto faced in the original story, like the Akatsuki's early interest in him. Also, Minato could introduce Naruto to the other powerful ninjas of the Hidden Leaf in a more personal way, which would change Naruto's relationships and his standing in the village.
One plot idea could be that Snape takes Hermione under his wing after he discovers her extraordinary magical potential at a young age. He secretly trains her in advanced potions and dark arts defense, much to the surprise of the other Hogwarts faculty. Another could be that Hermione's parents die unexpectedly, and Snape, having a soft spot for her intelligence, steps in as a guardian. He helps her navigate the complex wizarding world politics while she tries to uphold her muggle - born values.