Maybe Ron is angry because he has a long - standing feud with Draco. He sees Draco as the enemy from their Hogwarts days. So, seeing Draco married to his friend Hermione is like the ultimate betrayal in his eyes. He can't fathom how Hermione could be with someone he hates so much.
The cause of Ron's anger might be a combination of things. He might be jealous of Draco in general - his wealth, his pure - blood status. And on top of that, Hermione choosing Draco over him could shatter his ego. He was probably expecting that he and Hermione would end up together at some point, and this new situation completely goes against his expectations.
In this situation, the story could explore Ron's feelings of betrayal deeply. He might feel that Hermione has chosen the 'enemy'. Meanwhile, Dramione's relationship could be shown as a contrast to the chaos. They could be building a new life together, perhaps having a child on the way. This could be the thing that finally makes Ron realize that his anger is misplaced and that he should be happy for his former friend.
In some Dramione fanfictions, Ron might break up with Hermione because he feels overshadowed by her intelligence. He could be tired of always being in her shadow and decides to end the relationship. This then paves the way for a potential Dramione relationship as Hermione and Draco start to interact more.
It could be due to a misunderstanding. Ron might misinterpret Hermione's relationship with Draco. He could think there's something going on between them, especially in fanfiction where the Dramione pairing is the end goal. So, in his jealousy or anger, he decides to leave Hermione while she's pregnant without really understanding the situation.
A well-known Dramione fanfiction with this plot is 'Love's Betrayal'. Here, Ron's cheating triggers a series of unexpected events that bring Draco and Hermione closer together.
Another plot element is the exploration of Hermione's internal struggle. She has to deal with the shock of Ron's behavior and also the judgment from others. In some fanfics, the wizarding community might not believe her about Ron's abuse because of his status as a hero in the war. This forces Hermione to rely more on Draco, who, despite his own past issues, is more understanding in this fictional scenario. There's also often a build - up to a relationship between Draco and Hermione, which starts from mutual understanding of their difficult situations and grows into something more romantic.
In some fanfictions, Harry might be angry with Ron and Hermione if he feels they are keeping secrets from him. For example, if they discover something important about Voldemort's plans but don't share it right away, Harry could get angry. He's used to relying on them and when that trust is broken, even if it's a misunderstanding, his anger can flare up.
Another scenario could be that Hermione decides to keep the pregnancy a secret from most people. She might try to handle it all on her own, while still dealing with her feelings for both Ron and the unexpected situation. This could lead to a lot of internal conflict and self - discovery for her as she tries to figure out what she really wants in life.
One possible scenario could be that they have adventures together while also juggling their daily lives. For example, they might go on missions to protect the wizarding world from new threats, all while taking care of their family at home. Hermione could be using her intelligence to research new spells and potions, and Ron would support her and also contribute with his own skills and bravery.
Ash could be the cause. He might accidentally break a promise to Serena, like promising to watch her perform in a Pokemon Showcase but then missing it because he got caught up in a Pokemon battle. This would surely make Serena angry.
Harry would probably be curious about it in a way. He might secretly read some of it to understand why people are so interested in this pairing. Ron, on the contrary, would actively try to stop people from talking about it. He'd say it's disrespectful to Hermione and their friendship. He might even try to get Hermione to tell people to stop writing such fanfictions, but Hermione would likely be more understanding of the concept of fanfiction and not be as bothered as Ron.