They could be business partners in certain fanfic ideas. Imagine Dudley using his knowledge of the Muggle world and Harry his wizarding skills to start a business that caters to both magical and non - magical customers. This would require them to put aside their differences and work together, leading to a more amicable relationship.
Perhaps they could be neighbors in the fanfiction world. Living close to each other, they would have to interact. At first, it might be awkward, but over time, they could develop a sense of community. Dudley could help Harry with Muggle - related things like fixing a car, while Harry could use magic to do small favors for Dudley, like magically cleaning his house when he's in a hurry.
In some fanfictions, they might become grudging friends. As adults, they could start to understand each other's past traumas better. Dudley, having grown up and away from his parents' influence, might realize how unfairly he treated Harry as a child. Harry, on the other hand, might see Dudley's attempts at change and begin to trust him more.
In some fanfics, they might become reluctant allies. As adults, they could have grown out of their childhood enmity. Maybe Dudley has seen the real threats in the wizarding world through Harry's experiences and realizes they need to work together for the greater good.
In this fanfiction, they might start to become more like friends. Since Harry is helping Dudley eat better, there's a sense of care and concern that could be building a new bond between them.
Harry could become more relaxed. After all the battles and traumas of his youth, as an adult he might be more at peace. He could be less impulsive and more calculating. Dudley, having matured, might lose his bullying nature completely. He could be more empathetic, especially after experiencing some hardships in his own life that made him realize how his actions affected others.
It could be that Dudley has his own reasons to oppose the dark forces that are after Harry. He might see that if Harry fails, it could also mean trouble for him and his family. So, he decides to train Harry to fight as a way of self - preservation as well as helping Harry. Another reason could be that Dudley has grown to respect Harry over time and wants to contribute to Harry's ability to defend himself against the many threats he faces.
Dudley might face his father's anger. Vernon could be furious that Dudley has gone against him to protect Harry.
Well, it changes their relationship in that they become closer. Dudley's overprotective nature means he starts to see Harry as someone precious to him. This could lead to them sharing secrets. Harry might tell Dudley more about the wizarding world, and Dudley could confide in Harry about his insecurities. They might even team up against common enemies, like those who look down on both of them for different reasons. Overall, it makes their relationship more complex and interesting.
It could completely transform their relationship. If they have a positive reunion, they might become friends. They could start to support each other in different ways. Harry could use his magic skills to help Dudley out in small ways, like fixing something around his house without Dudley knowing it was magic. Dudley, in return, could offer Harry some insights into the Muggle world that Harry might not be fully aware of.
Harry could become more confident and self - assured as an adult. He has been through so much in his youth that he would have a strong sense of self. Dudley might become less of a bully. Maybe he has a family of his own and has learned to be more kind and patient, influenced by his own family life.
In the fanfiction, if Harry goes to Dudley's wedding, it could be a chance for them to finally fully reconcile. Maybe Dudley, who has grown up a bit, would introduce Harry to his friends as his long - lost cousin. Harry, on the other hand, could bring some magical charm to the event. He might perform a little magic trick for the kids at the wedding, like making balloons float without strings. This would make the wedding more fun and memorable.
Well, they might meet in a rather unexpected place. For example, Dudley could be on a business trip and end up in a town near where Harry lives. At first, they might not recognize each other. But when they do, there could be a flood of memories. They could end up having a meal together and during the meal, they start to really understand each other for the first time. Dudley could apologize for his past behavior, and Harry could accept it graciously.