A potential plot development might be that Voldemort, upon hearing that the Potters are alive, would be enraged and try to attack them again. This would lead to a new series of battles and challenges for Harry and his parents. They would have to work together to fight off Voldemort and his followers. Also, Harry's parents could help him unlock new magical abilities or knowledge that he didn't have access to before because they are more experienced wizards.
In such a fanfiction, Harry would likely be in shock. His world view has been centered around their deaths for so long. He could be hesitant to trust this new reality. But once he does, he'd have a whole new support system. His parents could teach him magic they've learned in their 'hidden' years. This would make him even more powerful and give him a different standing among his peers.
One way is that Harry discovers a spell that allows him to communicate with the dead. Using this spell, he contacts his parents. They give him advice on how to defeat Voldemort, like a secret weakness of the Dark Lord.
On a more magical level, reviving the dead is against the natural order of things in the wizarding world. This could attract unwanted attention from magical authorities or even dark forces. Some might see Harry's act as a dangerous precedent and try to either stop him or use his new - found power for their own evil purposes.
In this fanfiction, Harry might have a magical encounter where his parents' spirits guide him. Maybe they reveal secrets about his family's past that Dumbledore had been keeping from him for his own protection.
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.
One popular fanfiction could be 'The Potter Family Reunion'. In this, Harry's parents are alive and they have to deal with the after - effects of Voldemort's first defeat in a different way. It shows a more family - centered Hogwarts experience for Harry.
A fanfic with Harry's parents alive could have a plot where they discover a new threat to the wizarding world. Since they survived Voldemort's first attack, they are more vigilant. They raise Harry to be a strong wizard, teaching him both powerful spells and the values of the wizarding world. The story could involve them going on adventures together to find the source of this new threat. Along the way, Harry learns more about his family's history and his parents' experiences at Hogwarts. There would be a lot of family bonding and magical discoveries.
Well, it could be about Harry Potter finding a will left by his parents. Maybe in this fanfiction, the will contains secrets about his family, his heritage, or some sort of magical items or powers that were meant for him. It might also reveal things about his parents' past and their relationships with other characters in the wizarding world.
In a fanfiction where Harry's parents are alive, it could be that they were secretly protected by a powerful ancient magic. They were transported to a different magical realm. When they return, they bring with them new magical knowledge and spells. They help Harry become an even more powerful wizard. For example, they teach him how to combine different types of magic in unique ways. They also work to improve the relations between the wizarding world and other magical creatures.
The plot could be that Harry's parents are in a magically-induced coma. The Dursleys are tasked with looking after Harry until a cure can be found. Harry might feel a sense of isolation as he is with the Dursleys but constantly thinking about his parents. He could start to show early signs of magic, which terrifies the Dursleys even more, but also gives him hope that he can somehow use his powers to wake his parents up.