One possible plot development could be that they initially fight against each other as enemies, not knowing their relation. Then, through some kind of accident or revelation, they find out they are brothers. This could lead to a lot of internal conflict for both of them, especially for Deidara who has been on the 'wrong side' in the eyes of Konoha. Another development could be that there is a third party who knows about their relation and tries to use it for their own gain, forcing Naruto and Deidara to work together to overcome this threat.
Well, a likely plot development might involve their shared heritage. Maybe they both have some special power that is related to their family bloodline. As they discover they are brothers, they start to explore this power together. Also, there could be a plot where Naruto tries to 'save' Deidara from the path of evil that he has been on with Akatsuki. Deidara, on the other hand, could be conflicted between his loyalty to his Akatsuki comrades and his new - found brother. And perhaps in the end, they could work towards bringing peace between their respective villages.
Perhaps there could be a plot development where other characters react to Naruto's training with Deidara. For example, Sasuke might be suspicious or even jealous of Naruto's newfound skills. This could create tension between the two characters and lead to some exciting confrontations.
If Naruto were Samui's brother in fanfiction, it would likely lead to some interesting character interactions. For instance, Naruto might have a closer bond with the Cloud ninjas. He could also get involved in resolving internal issues within the Cloud Village. Maybe he would be more welcomed in the Cloud Village than in the original story. Additionally, it could affect his relationship with Sasuke, as he might have a new support system in the form of Samui and her comrades.
In this fanfiction, perhaps it's a story of redemption for Deidara. Naruto, as his brother, could be the one to show him a different path. They might go on adventures together, facing various challenges that test their relationship. It could also explore how their powers might be related or different, given their connection as brothers.
Well, in this fanfiction scenario where Naruto is Deidara's brother, it would be a huge shock to both the characters and the readers. Naruto has always been seen as a pure - hearted hero of the Leaf, and Deidara was a dangerous member of the Akatsuki. Naruto's character development could take a different turn. Maybe he would have a different view on the Akatsuki and their motives. He might even try to convert Deidara to the side of good, which would be a very interesting story arc. And his friends in the Leaf might be very suspicious of him at first, but Naruto would surely prove his loyalty in his own unique way.
In this fanfiction, a likely plot development could be that Naruto starts to experience strange visions or memories from Shisui's brother due to the Sharingan. This causes him to go on a journey to discover the secrets behind these visions. Also, the Leaf Village elders might become suspicious of Naruto's new power and try to keep an eye on him, which creates internal conflicts within the village.
One possibility is that Naruto's friends launch a rescue mission. They would use their unique skills, like Sasuke's Sharingan or Sakura's medical ninjutsu combined with her combat skills, to find and save Naruto.
I'm not sure of a specific 'naruto deidara is naruto's brother' fanfiction, but generally in such a concept, the fanfic could start by exploring how they were separated at a young age, perhaps due to some sort of conflict between the Hidden Leaf and Iwagakure. Then as the story progresses, they could discover their relation in a very dramatic way. This could then lead to them having to choose between their existing loyalties (Deidara to Akatsuki and Naruto to Konoha) and their new - found brotherhood.
One possible plot development could be Naruto facing internal struggles. He has always been Naruto Uzumaki, and now with Madara's DNA, he might question his identity. Another could be that the village starts to view him differently. Some might fear his newfound power, while others might see him as a potential threat. There could also be a plot where Naruto has to learn to control the new powers that come with Madara's DNA quickly, as an enemy emerges who can only be defeated with these new abilities.
In this 'naruto gets poisoned fanfiction', Naruto could also try to fight the poison using his own chakra. He might enter a state of inner struggle where he has to battle the effects of the poison on his body while still trying to protect the village. His Nine - Tails chakra could play a role, either helping him resist the poison or making the situation more complicated if it reacts badly with the poison.
One possible plot development could be that after saving Naruto, Madara tries to mentor him. He sees Naruto's potential and wants to shape him into an even greater ninja, sharing his own knowledge and skills that have been honed over years.