I can recommend the following novels, which all meet your needs. The plot of the heroine being adopted by her brother:
1. The female protagonist of this book was haunted by ghosts and eventually married her adopted brother. The male lead was the ruthless Mo King, and the female lead eventually became his girlfriend.
2. " 80 Lucky Lady ": The female lead was reborn as the Qin family's delicate lady. She was surrounded by Big Godbrother, Little Godbrother, and other brothers who doted on her.
3. " The Female Supporting Character in the Book Is Going to Counterattack ": The female protagonist has three brothers and a father, but she is the vicious supporting actress in the novel. She works hard to counterattack.
4. " Little Days of Miss General ": The female protagonist, Yang Yue, traveled to ancient times and lived a happy life after being adopted.
I hope you like the novels recommended above!
Luffy, of course. He and Sabo have a deep history. They grew up together and Sabo was like a brother to him. Their reunion would be filled with joy, hugs, and probably a lot of tears. Luffy would be over the moon to have Sabo back in his life and on his ship.
It could be a powerful pirate crew that has a vendetta against either Luffy or Sabo. Maybe they have some history with the Straw Hat Pirates or Sabo's group.
In a 'Sabo meets Luffy crew' fanfiction, there could be a lot of emotional reunions. Sabo might share his adventures since they last parted. He could train with the crew members, especially Zoro to exchange sword - fighting skills. And he would surely have a great time reminiscing about their childhood with Luffy.
One interesting scenario could be that they team up against a powerful new enemy. They combine their unique skills, Luffy's rubber abilities and Sabo's fire - based attacks, to create a formidable force.
A great Sabo meets Ace fanfiction might be the one where they meet in a parallel universe. In this universe, things are different but their brotherly love remains the same. They learn about the differences between their two worlds and how to make the best of their reunion.
One interesting story could be where Sabo and Ace reunite after a long time apart. They might share their adventures and catch up on old times. Maybe they team up to face a new threat in the pirate world.
I really like the fanfictions that involve Ace, Whitebeard and Sabo. They are such interesting characters. In many of these fanfictions, the relationship between them is explored in great depth. For example, how Sabo copes with having Ace as his 'brother' again after thinking he was dead. And Whitebeard's role as a father figure to them adds another layer of complexity and warmth to the stories.
His brother could be an unknown Uzumaki. Since Naruto is from the Uzumaki clan, it would make sense for his brother to be from the same clan. Maybe he was hidden away for some reason, like to protect him from the same threats that Naruto faced as a child.
Perhaps Naruto's brother could be a long - lost relative from a far - flung part of the ninja world. He could have been separated from Naruto when they were young due to a war or some political intrigue in the ninja clans.