It could also be due to broken promises. If his family made promises to him in the past, like always being there for him or protecting him, and then failed to do so, Naruto would feel betrayed. His journey to become a great ninja was filled with hardships, and if his family was supposed to be part of that support system but didn't come through, he may not be able to forgive them.
One possible reason could be years of neglect. Maybe his family was absent during his difficult childhood in Konoha, leaving him to fend for himself. He had to endure loneliness and the scorn of the villagers without any family support, which could lead to deep - seated resentment and an inability to forgive.
Well, perhaps in this fanfiction, Kushina did something that violated Naruto's principles. Naruto has always been about loyalty and hard work. If Kushina did something like betraying the village or his friends, Naruto, being the stubborn and principled person he is, might not forgive her. Also, it could be that Kushina was absent during some crucial moments in Naruto's life and he holds a grudge for that.
It could also be that his siblings continuously rejected him and his ideals in the past. Naruto has always strived for peace and acceptance, and if his siblings constantly opposed him on these fundamental things, it might lead to his unwillingness to forgive.
One possible reason could be that he feels abandoned. His parents died when he was a baby and he grew up without them. He might think that if they were more careful or made different choices, they could have been there for him. For example, if they hadn't gotten involved in the fight against Voldemort in a certain way, they might have survived. Another reason could be that he has heard so many stories about them but has no real memories of them. It's hard to forgive someone you don't really know but are supposed to have a deep connection with just based on what others say.
In the fanfiction, it could be that Sasuke's unyielding thirst for power and his disregard for the consequences of his actions on those around him are reasons Naruto doesn't forgive him. Sasuke was so focused on his own goals that he often trampled on the feelings and safety of others, and Naruto, who is all about protecting and connecting with people, may find it hard to forgive such self - centered behavior.
It could be due to miscommunication. In the fanfiction, perhaps there were misunderstandings within the family. For example, Naruto might have overheard something that made him think his family didn't have his best interests at heart, but in reality, it was all a big mix - up. So, he gradually lost trust in them.
One possible reason could be a misdirection in his goals. If in the fanfiction he is overly focused on proving himself to the village, he might think that family is a distraction. So, he starts to distance himself from his family to concentrate more on getting recognition from the village.
It could also be due to Sakura constantly doubting Naruto's abilities in the story. Naruto has always been looked down upon by many in the original series, and if in the fanfiction Sakura continuously expresses her lack of faith in him, it could lead to his unforgiveness. For example, she might have refused to believe in Naruto's new jutsu or his plans to save the village, which made Naruto feel really disappointed and unable to forgive her.
One possible reason could be past betrayals. Maybe he has been let down by people he thought were friends in the fanfiction world. For example, if someone he trusted shared his secrets which led to him getting into trouble.
Perhaps in the fanfiction, Naruto is exposed to a new philosophy or way of thinking that promotes forgiveness. He might meet a wise character who teaches him about the power of forgiving one's family. Also, if Naruto experiences a similar situation where he has to make a tough choice that might be misjudged by others, he could then understand his family better and forgive them. It could also be that Naruto finds out his family had no other option in the situations they were in, and this realization leads to his forgiveness.
One possible reason could be that Naruto has had some past experiences within the team that made him feel betrayed or let down. Maybe there was a mission where he thought his teammates didn't have his back. Another reason might be that there are secrets among the team members that Naruto has discovered, and these secrets make him question their loyalty. For example, if one of his teammates was hiding a connection to an enemy, Naruto would naturally start to lose trust.