He might be more old - fashioned in his ways. His grandparents' values would likely have a big influence on him, so he could be more reserved and traditional compared to the Harry we know from the original series.
One idea could be that his grandparents are very strict about magic, so Harry has to secretly practice it. He might discover some old family magic that his grandparents were unaware of.
In this kind of fanfiction, perhaps Harry would grow up with a different kind of family warmth. His grandparents might be more traditional and instill in him values that are different from what he would have learned at the Dursleys. He could be more connected to the wizarding world's history as his grandparents might have more stories to tell from the older days. Maybe he would be less bullied and more confident, and his magical abilities could develop in a more natural and unrestrained way.
One idea could be that his grandparents, being more experienced in the wizarding world than the Dursleys, start teaching Harry magic early on in a more positive and nurturing way. Maybe they introduce him to family secrets and spells that have been passed down through generations.
He would likely be more confident. Growing up with his grandparents, who presumably love and support him, he wouldn't have the self - doubt that came from living with the Dursleys. He would be more self - assured in his magical abilities from the start.
One plot idea could be that Harry's grandparents are very strict about magic, so he has to secretly practice. Another could be that they are part of a secret wizarding society that has been in hiding, and Harry discovers their secrets. Or perhaps they have a special connection to Voldemort's past that Harry uncovers.
Perhaps his grandparents were great adventurers in their time. They could have traveled to far - off magical lands and encountered strange and wonderful things. Their experiences could be passed on to Harry, inspiring him to explore more of the wizarding world and its secrets. They might also have been involved in some great battles in the past, and their war stories could give Harry valuable lessons for his own fight against Voldemort.
They could be very traditional and strict pure - blood wizards. Maybe they were part of some ancient magical order and had high expectations for the Potter family. They might be disappointed in how James and Lily Potter deviated from some of the old ways, but be very proud of Harry when they get to know him.
If Harry was raised by his grandparents in fanfiction, his personality would change in several ways. For starters, he would be more self - assured because he'd grow up in a loving environment. He wouldn't have the same insecurities that came from being treated as an outcast at the Dursleys. He'd be more extroverted, as he wouldn't be afraid to show his true self. His sense of humor might be different too, perhaps more light - hearted and less sarcastic as a defense mechanism. He'd also have a stronger sense of family and heritage, which would influence his actions and decisions.
If Harry Potter meets his grandparents in a fanfic, it could be a life - changing encounter. His grandparents would likely be shocked and overjoyed to see him. They might be able to fill in the gaps in his knowledge about his family history. They could have known some secrets about the prophecy related to Harry and Voldemort that could help him better understand his destiny. They might also be powerful wizards or witches in their own right and offer to train Harry further in magic, especially in areas that Dumbledore or other Hogwarts professors hadn't covered. Their presence could also give Harry a sense of belonging and family that he had been missing all his life.