Their family backstory could be that their parents were both outcasts in their respective worlds. The Naruto - world parent was shunned for having different ideas about chakra use, and the Fairy Tail - world parent was an outcast because of their unique view on magic. They found solace in each other when they accidentally ended up in a neutral dimension. There, they built a home and had Naruto and Natsu. The family was constantly on the move to avoid those who would persecute them for their differences. As Naruto and Natsu grew, they carried the hopes of their parents to create a world where both ninjutsu and magic could coexist peacefully, and their family backstory would be one of perseverance and the search for acceptance.
Yes, in certain fanfictions Natsu and Wendy are considered siblings. This could be due to various reasons. Maybe the author wants to explore a different family dynamic within the Fairy Tail world. It can add an interesting layer to their relationship, like how they support each other more like family members would. Also, it might change the way they interact with other guild members as well.
In this fanfiction world, Naruto's chakra and Natsu's magic could coexist because they are different manifestations of energy. Naruto's powers are more about internal energy manipulation within his body and using hand signs to release various techniques. Natsu's power comes from eating magic and is more instinctual. Their family could be seen as a bridge between two different power systems. It could be that their family has a special role in maintaining the balance between ninjutsu and magic in the overall fictional multiverse they exist in.
In some fanfictions, the siblings could be entirely new characters created by the author. They might have unique ninja abilities like one sibling could be a master of wind and water jutsus combined. Another could be a prodigy in genjutsu, stronger than Sasuke in that aspect. And the third might be a non - combatant sibling who is more into the political and diplomatic side of the ninja world, helping Naruto in a different way than fighting.
In some fanfictions, they might be reimagined as siblings. Fanfiction allows for a lot of creative interpretations. However, in the original Naruto series, they are not siblings but comrades.
Well, it's quite possible. Fanfiction writers are known for their wild and creative ideas. Since both Naruto and Natsu are from popular anime, some writer might have thought of creating a story where Naruto is somehow related as Natsu's grandfather. But it also depends on how much of the respective anime universes the writer wants to blend and how they would explain such a connection in the story.
Yes, there are likely fanfictions out there with such a concept. Fanfiction platforms are full of creative and often wild ideas. You can check major fanfiction websites like FanFiction.net or Archive of Our Own (AO3). Just search for the relevant tags or keywords to find them.
Their relationship can be developed by having them share more personal stories about their past with the dragons. For example, Natsu could tell Wendy about Igneel's funny habits, and Wendy could share her memories of Grandeeney. This would strengthen their bond as siblings who share a common dragon - slayer heritage.
One possible relationship is that of a mentor. Naruto, with all his skills and experiences, could be like a mentor to his siblings. He would teach them ninja techniques and how to face the challenges in the ninja world.
Well, Naruto is known for his positive energy. In this fanfiction, he could show his love for his siblings by bringing that positive energy into their lives. He would cheer them up when they are down, encourage them when they face difficulties. He might also cook for them or do some small but meaningful things, like helping them with their training or just listening to their problems.