In fanfiction, the idea of Naruto being Itachi's half - brother might be based on some creative reinterpretation of the clans. Suppose there was a long - lost connection between the Uzumaki and the Uchiha clans. This could potentially lead to a situation where Naruto and Itachi share a half - brother relationship. However, it's important to note that this goes against the canon story. The beauty of fanfiction is that it allows for these kinds of 'what - if' scenarios.
In a fanfiction context, it could be possible through some creative plot devices. Maybe a powerful jutsu was used that altered their memories or destinies. For example, a rogue ninja with a forbidden time - bending jutsu made them believe they were in love and got married. It could also be due to some sort of political alliance gone wrong in a strange way, where they were forced into a marriage - like situation and over time, developed real feelings for each other.
In fanfiction, the idea of Naruto having a son with Itachi might be part of a complex AU (alternate universe). The story could set up a world where the Uchiha and Uzumaki clans have a different relationship. Itachi, instead of following his original path, gets involved with Naruto in a way that leads to the birth of a son. This could be due to political alliances, or a new prophecy in this alternate Naruto universe that binds their fates together.
The half - brother could be developed as a character with a troubled past. He might have been ostracized in his own community because of his relation to Naruto or his own unique abilities. This could make him initially cold and distant but as he interacts with Naruto, he could gradually open up and become more warm - hearted.
Well, in the official Naruto universe, it's highly unlikely. Naruto and Itachi come from different clans and have very different relationships within the story. Naruto is focused on his own goals and relationships like with Hinata, and Itachi has his own complex story with Sasuke. However, in the world of fanfiction, anything can be made possible as it allows for creative interpretations and alternative storylines that deviate from the original canon.
It's not really possible within the normal Naruto lore. But fanfiction is all about exploring 'what ifs'. In a yaoi fanfiction where Naruto brings Itachi back to life, it could be based on some extreme emotional bond. Maybe Naruto discovers a hidden power within himself that he can use to reverse death. But this goes against the established rules of the Naruto world where death is usually final. So, it's really a matter of the author's creativity and how they can justify such a huge event within the framework of the Naruto world, even if it's a yaoi - inspired take on it.
One way this could work is if there was a shared ancestry that was hidden or lost over time. Perhaps there was an ancient clan that had members in both the Naruto world and the Fairy Tail world. Through some convoluted plot device in the fanfic, Naruto and Erza could be discovered to be part of this long - forgotten clan, thus making them siblings.
It could also be that Naruto has been influenced by Itachi's self - sacrifice. He saw how Itachi sacrificed everything for the greater good. So, in the fanfiction, Naruto might secretly work for Itachi as a way of carrying on his legacy. He may be helping Itachi from the shadows to achieve goals that Itachi was unable to complete during his lifetime.
In the realm of fanfiction, this situation might be crafted to explore deeper emotional and relationship aspects. The writer could be using this as a way to show a complex relationship between Naruto and Itachi. It could be that in this fanfic's universe, there are new types of chakra or abilities that make this pregnancy possible. For example, a special chakra bond between them that defies the normal biological limitations of the Naruto world. It also might be a means to shock the readers and draw them into a story that challenges their preconceived notions about the characters.
It could be a complex plot where Naruto, disillusioned with the shinobi world for some reason, decides to create a new identity as the Masked Man. He might have seen too much corruption or pain and believes that by operating from the shadows as the Masked Man, he can bring about real change. He could be using the mask as a symbol to strike fear into those who are causing harm, while also trying to protect the ones he loves without them knowing it's actually him.
If Naruto were Itachi's older brother in fanfiction, the power dynamics in the Uchiha clan could be very different. Naruto's influence might prevent the Uchiha massacre. He could use his positive and determined attitude to change Itachi's view of the village. Also, Naruto's relationship with Sasuke would be completely redefined, as he would be Sasuke's older brother's older brother. This could lead to a more united front against the real threats in the Naruto world.