First, his character could start off as a bit of an enigma. Maybe he has been away from Hermione for a while, and when he returns, he realizes how much she needs protection. As the story progresses, he could show his protective side more and more. He might be a strong wizard, but also have a soft heart, especially when it comes to Hermione. He could be developed as someone who is well - respected in the wizarding community for his own achievements, and uses that status to shield Hermione. For instance, if she's wrongly accused of something, he uses his influence to clear her name. He could also have a bit of a temper when it comes to those who threaten Hermione, which adds an interesting dimension to his character.
Well, he could be developed as a more introverted character compared to Ash. Instead of being as outgoing and eager to make friends, he might be more focused on his research of Pokemon, like studying their behaviors or habitats. This would make him a unique character with his own set of goals and values.
A possible plotline is that the older brother, having graduated from Hogwarts before Hermione, has a lot of connections in the wizarding world. When Hermione starts getting involved in the fight against the Dark Lord, he uses these connections to protect her. He might get her access to powerful protective spells or magical items that are not easily available. He could also be a bit of a maverick and not fully trust Dumbledore. So when Hermione is blindly following Dumbledore's orders, the brother steps in to make sure she's not being led into unnecessary danger. For instance, if Dumbledore sends Hermione on a dangerous mission, the brother might try to find an alternative way to achieve the same goal without putting her in harm's way.
Hermione might become more confident in her Slytherin - like traits. Since Blaise is her brother, she could learn from his Slytherin ways of being cunning and resourceful. This would add a new layer to her Gryffindor - centered character.
He could be really curious. Just like Hermione is always eager to learn new spells and knowledge, he might be constantly exploring the Hogwarts grounds, looking for hidden secrets or new magical creatures.
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.
It could make Hermione more confident. Knowing she has an older brother might give her a sense of security, so she could be more assertive in her friendships. For example, she might be more likely to stand up to Ron when they have an argument, because she has that family support in the back of her mind.
Often, he is brave. Just like Harry himself, he doesn't shy away from danger when it comes to protecting his younger brother. For instance, he might stand up to Voldemort's followers without hesitation.
In the fanfiction, the older brother could change Naruto's view of his family and his place in the world. Naruto would have a connection to his past that he didn't know before. This could lead him to explore more about the Uzumaki clan and discover hidden powers or knowledge. And it could also affect his relationships with Sasuke and Sakura. For instance, his brother could help him understand Sasuke's pain better, leading to a different dynamic between them.
At Hogwarts, Harry would have someone to look up to within his family. This could boost his self - esteem. His older brother could be popular, and through that, Harry might gain more friends. Also, they could team up in Quidditch, making Gryffindor's team even stronger.
Maybe they embark on a journey to rescue a captured wizard or witch. They use their different strengths - Hermione's strategic thinking and her brother's charm or ability to make quick friends in the wizarding world - to plan and execute the rescue mission.