The main characters are Dudley and Harry. Dudley, who has usually been portrayed as a bully in the original series, is now the hero. Harry, on the other hand, is the target of whatever danger is present in the fanfiction. There might also be other supporting characters like Dudley's parents or some of Harry's friends from Hogwarts who could play a role in the story.
Perhaps Dudley finally stands up to his father's cruel treatment of Harry. Maybe he realizes that Vernon's behavior towards Harry is wrong and uses his own physical strength or some clever ruse to get Harry out of a difficult situation Vernon has put him in.
One possible plot point could be Dudley finally realizing the true nature of the danger Harry is in and using his new - found courage to save him. Maybe he discovers some secret about Voldemort that helps him protect Harry. Another could be Dudley using his physical strength, which he was known for in the original series in a more heroic way to fend off Death Eaters.
Well, perhaps Dudley uses his street - smart knowledge. He might teach Harry some rough - and - tumble moves he's learned from his own scuffles in the neighborhood. For example, showing Harry how to dodge a punch quickly.
Harry might become more open and less guarded. Since he now has a brother in Dudley, he might feel more at home in the Muggle world. Dudley, on the other hand, could become less of a bully. The knowledge that he has a wizard for a brother could make him more humble and empathetic.
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.
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.
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.
I'm not sure if there is a specific 'Dudley Gets Harry mpreg fanfiction'. Fanfiction covers a vast range of ideas and pairings, but this one seems rather unusual. It might exist in the extremely diverse world of fan-created works, but it's not a common or widely - known type of fanfiction. You could try searching on specialized fanfiction websites to find out for sure.