The evolution of their relationship in the fanfic could be complex. Dudley has a history of being cruel to Harry. But time has passed. Dudley may have realized the error of his ways through his own life experiences. When they meet again, Harry will be cautious at first. However, if Dudley shows sincere remorse and a willingness to change, Harry will gradually let his guard down. They could start to share common interests, perhaps in sports (Dudley's love for boxing and Harry's love for Quidditch in a way). This could be the foundation for a new, more positive relationship.
Their relationship could evolve positively. Dudley could have grown out of his mean - spirited ways and become more empathetic. He might be in awe of Harry's wizarding abilities now. Harry, seeing Dudley's change, would be more open to him. They could start to support each other, like Dudley helping Harry with Muggle - related things and Harry protecting Dudley from any magical threats.
It depends on how much Dudley has changed. If he's still a bit of a bully at heart, there could be initial tension. But if he's truly reformed, they could become friends. They might go on adventures together in the Muggle world or Harry could introduce Dudley to some of the more friendly aspects of the wizarding world, like the Weasley's joke shop. Their relationship could grow into a unique bond that combines both Muggle and wizarding elements.
They might finally have a real heart - to - heart conversation. Dudley could apologize for all the bullying in the past. Harry, being the forgiving person he is, would accept it. Maybe they'd end up becoming friends and sharing stories about their different lives since they parted ways.
Well, Harry and Dudley's relationship would change drastically. Harry, by adopting Dudley's child, is taking on a huge responsibility. Dudley might initially be in denial about the whole situation, but as time passes, he realizes that Harry is providing a better life for his offspring. This could lead to a thaw in their long - standing animosity. Harry might start to view Dudley as someone who has made mistakes but is also trying to do right by his child in his own way. And Dudley could start to view Harry as a real family member, someone he can rely on.
A scenario where Dudley has somehow gotten involved with the wizarding world on his own. Maybe he found a magical artifact and was trying to figure out what to do with it when Harry shows up. This would force them to interact in a completely new way, with Dudley now being in Harry's territory so to speak.
They might finally make peace. In many fanfictions, Dudley has grown and realized how wrongly he treated Harry in the past. So when they meet again, they could start to have a normal conversation, maybe even become friends or at least be civil to each other.
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 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.
It could develop very smoothly. They already have a strong foundation of love, so when they meet, they just pick up where they left off and become even closer.
At first, it might be a bit awkward as they get to know each other. But then they would grow closer. His grandparents would probably dote on him and Harry would come to rely on their love and support.
It could develop into a more tolerable one. Harry might start to see Aunt Marge as a pitiful figure rather than just a mean old woman. Maybe he discovers some things about her past that make him more empathetic.