One possible fanfiction idea could be that Hinata's twin brother is a prodigy in a different ninja art than Hinata. He might be more focused on offensive taijutsu techniques, while Hinata is known for her gentle fist. This could create an interesting dynamic within the Hyuga clan as they both grow and develop their skills.
The plot could involve Naruto protecting Hinata from the Hyuga clan's strict traditions. Since he's not bound by those traditions as her brother, he could fight against the elders who want to keep Hinata in a subservient role.
I'm not sure of a specific 'Naruto brother of Hinata' fanfiction off the top of my head. However, many fanfictions in this vein might focus on how Naruto, as Hinata's brother, could influence her confidence and her relationship with other characters. For example, he might play a more active role in helping her with her training or dealing with the Hyuga clan politics.
Well, the plot could be that Hinata's twin brother is sent on a secret mission. He discovers a conspiracy within the village that could threaten the Hyuga clan. He has to gather evidence and allies, and Naruto could be one of the key allies. They might have to fight against some rogue ninja who are part of the conspiracy.
The original Naruto story would be turned upside down. Naruto being Hinata's twin would affect his relationship with Sasuke too. Maybe instead of his intense rivalry with Sasuke, Naruto would focus more on family matters. His dreams might also change as he would be part of the Hyuga clan. The Hyuga clan's secrets and techniques could be shared with Naruto more easily. This would give him an edge in battles and change how he approaches his ninja career. His friends like Shikamaru and Kiba might view him differently as well, since he would now be associated with the Hyuga clan rather than just being the orphaned Uzumaki.
In some Naruto fanfictions, Hinata could potentially be portrayed as a 'weapon' in a very metaphorical sense. For example, her Byakugan abilities might be exploited in unique ways that make her seem like a strategic weapon for a side or a cause. But in the canon Naruto story, she is a character with her own agency and not really a weapon.
One great source for Naruto and Hinata fanfiction could be FanFiction.net. You can search for stories specifically focused on their relationship there. There are often new and interesting takes on their story, from how they first fell in love to their married life in the future.
Perhaps in the fanfiction, Hinata wears a micro bikini for a special festival in the Hidden Leaf Village. Naruto is really excited to see her in it. They participate in the festival games together and Hinata's new look makes Naruto see her in a different light, more as a strong and confident woman.
If Naruto and Hinata were twins in a fanfiction, their combined strength could be formidable. Naruto has his vast chakra reserves and the Nine - Tails' power. Hinata has the Byakugan and her gentle fist technique. Together, they could use Hinata's Byakugan to scout and plan attacks while Naruto uses his brute force. They could also combine their chakra in some unique ways, perhaps creating new jutsu. Their teamwork would be enhanced due to their twin bond, allowing them to anticipate each other's moves better.
One possible fanfiction could involve Naruto learning kenjutsu skills and Hinata being inspired by his newfound abilities. Maybe Naruto discovers an ancient sword technique and Hinata supports him in his training, leading to a deeper bond between them.