In a fanfiction where Lily and James Potter are alive, the plot would be turned on its head. For starters, the Dursleys would never have come into the picture. Harry would have been raised in a loving magical family. This would mean he'd have access to all his magical knowledge and abilities from a young age without any suppression. Also, the war against Voldemort would have been fought very differently. Lily and James, being experienced and powerful wizards, would have led the charge. Their presence would have inspired a different kind of hope in the wizarding community. And think about Hogwarts - Harry would be going to school with his parents' support and influence, which could change how he interacts with his classmates and teachers.
Harry would grow up with his parents, which means he would have a much more stable and loving childhood. He would not have to face the Dursleys' abuse. His parents could teach him magic from a very young age, so he might be more advanced in his magical abilities. Also, he would have a strong family support system, which could make him more confident and less self - doubting.
Harry would likely be more confident. With his parents alive, he would grow up with their love and support, not having to face the same insecurities. He might be less impulsive as he would have their guidance. For example, he wouldn't have to jump into dangerous situations alone as he'd have his parents to back him up.
They change it a great deal. For starters, Harry wouldn't be an orphan. He would grow up with his parents, which would completely change his personality. He might be more confident and less brooding. Also, the whole dynamic of the wizarding world would be different. There would be no need for Dumbledore to have as much control over Harry's life. James and Lily could have their own influence on how the wizarding world is run.
The plot would change a great deal. For one, Harry wouldn't have to live with the Dursleys. He would grow up in a loving magical household. He'd be more confident and perhaps less of an underdog. His parents would be able to train him in magic from a young age, so he might be more advanced in his studies when he gets to Hogwarts. Also, the fight against Voldemort would be a family affair, with James and Lily Potter being key players in the battle against the Dark Lord.
In such fanfictions, the lack of parental support means Harry might form different relationships. For example, he could rely more on his friends or other adult figures like Sirius or Remus in a different way. The dynamic at Hogwarts could also change. Without the influence of his parents' love, he might be more vulnerable to the taunts of his classmates, which could lead to a darker path for his character. He could also be more desperate to prove himself, which might make him take more risks.
A lot of fanfictions in this category might explore different timelines. For instance, some might have them survive the initial attack and then change the course of the wizarding war. They could use their combined magical powers to turn the tide early on. So, look for stories that focus on these aspects when you search for fanfictions about them being alive.
A really interesting plot could be that James and Lily, alive, work with Dumbledore to create a new school of magic. This school would focus on teaching students how to defend against the Dark Arts in a more practical and hands - on way. Harry would be one of the first students there. They could also develop new magical artifacts that could help in the fight against evil. And the family could have adventures all over the world to find the ingredients and knowledge needed for these new creations.
One interesting plot idea could be that Lily and James, alive and well, decide to train Harry in magic from a very young age. This would make Harry an even more powerful wizard earlier on. They could also use their influence to reform the wizarding world, starting with Hogwarts. For example, they might introduce new courses that focus on both light and dark magic, teaching students how to defend against the dark arts in a more comprehensive way.
Well, if James and Lily are alive, Harry doesn't grow up an orphan. He has his parents to guide him. For instance, he might not go to Hogwarts with the same sense of longing for family as he does in the original. His character development would be different as he has a loving family environment.
He'd be more confident. With a loving mother around, he wouldn't have the insecurities that came from growing up with the Dursleys.