shoto finds out dabi is his brother

One common theme is redemption. Dabi, with his troubled past, often has a journey towards redemption, and Shoto can play a part in that. Another theme is family. Given their complex family relationships in the original story, fanfics often explore how they deal with family issues together.

There's also 'The Unlikely Bond'. In this fanfic, Dabi and Shoto start off as enemies but gradually find common ground. It has some really interesting character development and plot twists that keep you hooked.

Maybe a magical accident or a powerful spell that revealed the truth.

Harry would likely be stunned. His world has been turned upside down. He might initially be in denial, thinking it's some sort of cruel joke or a mistake. But as he starts to accept it, he may feel a new sense of connection to Blaise. He could start to see Blaise in a whole new light, noticing similarities in their personalities or abilities that he hadn't before. And he would probably be eager to learn more about their shared heritage and what it means for their future together.

The brother could be embarrassed at first. He might try to play it off as a joke or just avoid the topic altogether.

For Merlin, there are both good and bad consequences. On the bad side, some of the more traditional and anti - magic people in Camelot might try to oppose him. However, since Arthur now knows, he has a powerful ally. Arthur can protect Merlin from those who would do him harm. Also, Merlin can now be more open about using his magic for the good of Camelot, which is a positive change.

I'm not sure if 'his wife is story' is a correct expression. It might be a misprint or an unclear statement. If you mean 'his wife is a storyteller', then it means his wife likes to tell stories. If it's something else, more context is needed.

Some of his other friends might react differently too. Some may be more cautious around him, worried about the power of the jinchuuriki within him. But those who truly trust Naruto, like Shikamaru, might not change their attitude much. They would see that Naruto is still the same person he was before, just with this added aspect to his identity.

His confidence would probably soar. Knowing he has his parents, who are likely strong ninjas, supporting him would make him feel more secure. He might become a bit less reckless as he now has people who care about him deeply and he wouldn't want to worry them.

His friends might be shocked too. They could be supportive of Harry, trying to help him come to terms with this new information. For example, Hermione would probably start researching if there was any way to change this in the magical world's past, while Ron would be more about just being there for Harry, sharing his feelings.