Maybe there are secrets in the family. For example, his parents might be involved in some dangerous and secretive missions that require them to keep their distance from Naruto to protect him, but Naruto misinterprets it as neglect.
It could be due to a family curse or some special family circumstances. Perhaps there is an old family rule or a prophecy that forces his family to treat him coldly. For instance, they might believe that by neglecting him, they can prevent some great disaster from happening.
One possible reason could be that they are too focused on their own problems or duties. Maybe they are involved in some important shinobi business that takes up all their time and attention, causing them to overlook Naruto.
One possible reason could be jealousy. If Naruto has the rare Mokuton ability, his family might be jealous of his potential power and neglect him out of spite.
It could also be due to some family curse or prophecy. In the Naruto universe, there are often strange powers and curses. Maybe there was a prophecy that said Naruto's family had to keep their distance from him to protect him from some greater evil. So, they chose to neglect him in order to keep him safe, even if it was a difficult choice.
One reason could be that his siblings have some special abilities or talents that overshadow Naruto. In the ninja world, those with unique powers often get more attention. So, if his siblings possess something extraordinary, Naruto might be pushed to the side.
One possible reason could be that they are too involved in their own shinobi duties. The world of ninjas is full of dangerous missions, and they might be constantly away on important tasks, leaving Naruto feeling neglected.
He might focus on his training more. By pouring all his energy into getting stronger, he can distract himself from the pain of family neglect. For example, he could spend long hours practicing new jutsu or improving his physical abilities.
Maybe he's been influenced by someone who has a different view of heritage. For example, if he meets a character who believes that one should create their own identity rather than relying on heritage, Naruto could be swayed. Another possibility is that he has some sort of resentment towards his heritage. Perhaps there are things in his family's past or in the traditions associated with his heritage that he doesn't agree with or is ashamed of.
In this kind of fanfic, Naruto might first feel a great deal of sadness. He could start to distance himself from his family. Maybe he focuses more on his training, pouring all his energy into becoming stronger so that he can prove himself without relying on his family's recognition.
He may also seek solace in his friends. Since his family is neglecting him, Naruto would likely turn to his friends like Sasuke and Sakura. They become his new 'family' in a sense, providing the support and love he doesn't get at home. He shares his feelings with them and they encourage him to keep going, which helps him deal with the pain of neglect.
He might develop them through self - discovery. Maybe he stumbles upon some old scrolls or has a natural inclination towards it that he nurtures on his own.