Responsibility is a common theme. As an older brother, Naruto has to take care of others. Another theme is protection. He needs to protect his siblings from various threats in the Naruto world.
In 'older brother naruto fanfic', a prevalent theme is family bonds. It shows how the presence of an older brother can strengthen Naruto's sense of family, which he lacked growing up. This often leads to Naruto becoming more confident and having a better understanding of his place in the world. Also, the theme of self - discovery is common. Through his interactions with his older brother, Naruto discovers new aspects of himself, his powers, and his potential. It's like the older brother acts as a catalyst for Naruto's personal growth. Additionally, themes of loyalty and sacrifice are also seen, as the older brother is willing to do anything for Naruto.
One common theme is protection. The older brother is often depicted as protecting Naruto from various threats. Another theme is mentorship, where the older brother guides Naruto in his ninja training.
In this fanfic, Naruto could be a protector for Grayfia. Since he is her older brother, he would feel responsible for her safety. Naruto's ability to sense danger and his combat skills would be useful in Grayfia's often - dangerous world. Also, their different upbringings could lead to interesting cultural exchanges. Naruto, from a ninja village, and Grayfia, from a magic - based society, could learn a lot from each other's lifestyles and traditions.
I'm not sure if there is a specific fanfic with that exact premise. However, in the Naruto canon, Naruto has no such relation to Tsunade. Fanfic writers might create such a story for the sake of exploring different character dynamics and plot twists. They could potentially rewrite the backstories to make it work, like having Naruto be from a different family lineage that is related to Tsunade's in some way.
One popular 'naruto older brother fanfic' is 'The Older Brother's Influence'. It shows how an older brother figure in Naruto's life could have changed his training and relationships. Another one might be 'Brotherly Bonds in Konoha' which delves into the unique bond an older brother could have with Naruto within the village.
The older brother in the fanfiction might be a character with a tragic past. For example, he could have been experimented on by Orochimaru and gained some strange powers as a result. And he returns to the village later to protect Naruto from the threats that are coming towards him.
Yes, in some fanfics, Harry can be depicted as James' older brother. Fanfic writers often like to play around with the family relationships in the Harry Potter universe to create unique storylines.
It would probably be full of interesting interactions. Naruto's energetic and determined nature would contrast with Erza's more serious and disciplined personality. There could be scenes where Naruto protects Erza or teaches her some of his ninja skills.
One popular 'naruto the older brother fanfic' could be 'Naruto's Big Brother Adventure'. It often shows Naruto in a different light as he takes on the role of an older brother figure. Another one might be 'The Older Brother Naruto', which explores how Naruto's character would change if he had to be more responsible in that role.