Perhaps the grandfather is a wizard who was wrongly accused of some dark deeds in the past and had to go into exile. But he's actually a good man. When he found out about Harry's situation, he decided to come out of hiding and raise Harry, teaching him the truth about the wizarding world and how to avoid the same kind of false accusations in the future.
The grandfather might be a relative from Harry's mother's side. He could be a pure - blood wizard who has a vast estate and a lot of knowledge about the old magic. He might have been waiting for the right moment to take Harry under his wing and now that the opportunity has come, he's ready to raise Harry as his own.
It could be an old and powerful wizard who has been in hiding for years. Maybe he was a friend of Dumbledore's but had some differences with him, so he stayed away from the main events in Harry's life until now.
Well, perhaps the grandfather could be teaching Harry all kinds of magic that his parents didn't have the chance to. He might introduce Harry to a different side of the wizarding world, full of old family secrets and forgotten spells.
His grandfather could be a very strict and traditional ninja. He might have high standards for Naruto in terms of ninja skills and discipline.
They might be similar in appearance. For example, they could have the same eye color or the shape of their nose.
One possible plotline could be that Harry's grandfather imparts unique magical knowledge to him that he doesn't get at Hogwarts. Maybe it's an old - fashioned kind of magic that has been forgotten over time. This could give Harry an edge in dealing with the dark forces.
He could be a powerful and respected shinobi from the Uzumaki clan. Given the Uzumaki's reputation for strong chakra and unique abilities, Naruto's grandfather might have been a key figure in the clan's history.
There could also be other characters like Harry's friends, such as Ron and Hermione. They might be involved in the story and notice the similarities between Harry and his grandfather, and through their reactions, the story could unfold in different ways.
One possible plot could be that his grandfather, perhaps a powerful but reclusive wizard, trains Harry in unique magic from a young age. Harry might grow up with a different set of values and skills compared to the original story. He could have a closer bond with the wizarding world's older traditions.
To start a 'Harry Raised Grandfather' fanfic, begin with character development. Figure out what kind of person Harry's grandfather was originally and how Harry's presence will change him. Then, create a plot outline. Maybe start with Harry arriving in the past in a dramatic way, like through a mysterious portal. After that, think about the conflicts that will arise. For example, how will the wizarding community of that time react to Harry's strange ways? And don't forget to add some emotional moments, like when Harry and his grandfather have a heart - to - heart talk about family values.
There could be a 'Harry Raised Grandfather' fanfic where Harry is magically sent back in time due to a botched spell. He then finds his young grandfather in a difficult situation. Harry decides to take him under his wing. The fanfic could detail their relationship growth, like how Harry teaches his grandfather about the importance of love and friendship, which in turn shapes the grandfather into a different person, ultimately changing the course of the Potter family history.
Harry could develop a more unique style of magic. His grandfather might have his own way of doing magic, and Harry would learn from that. For example, his grandfather could be more in tune with nature magic, and Harry would then incorporate that into his spell - casting, making his magic more diverse and less reliant on the traditional Hogwarts curriculum.