Some writers might create such fanfiction for the shock value. They want to break the established strong friendship in the original series to get readers' attention.
I don't think it's very popular. Most 'Harry Potter' fans are attached to the original relationships and storylines. Cheating is not a theme that is associated with the main characters in the way the books are written, so this kind of fanfiction would likely go against what most fans expect and enjoy.
Harry might react with shock. If he overhears something unexpected like Ron and Hermione confessing their love for each other, it would be a big surprise. He might stand there frozen for a moment, not knowing how to process it.
In the Harry Potter movies, Harry was very close to Ron and Hermione. The three of them grew up together and experienced many adventures, establishing a deep friendship between them. In the movies, Harry and Ron were usually closer because they got along more naturally and frankly. The relationship between Harry and Hermione was even more complicated and special because they had a deep friendship and emotional entanglement. The interaction between Harry and Hermione throughout the movie was also very exciting and touching. Therefore, both Harry and Ron and Harry and Hermione's relationship were very impressive.
In the Harry Potter movie, Harry, Ron, and Hermione were three good friends who were very close. They had experienced many adventures and faced many difficulties together, and they supported and encouraged each other. The friendship between the three of them was an important theme in the movie, showing one of the best aspects of human nature.
In the Harry Potter movie, Harry, Ron, and Hermione were good friends and had a very good relationship. There was a strong brotherhood between the three of them. They always supported and helped each other in the face of difficulties and challenges. In the movie, the brotherhood between Harry and Ron was even deeper, and Hermione was one of Harry's best friends. She and Harry had similar backgrounds and experiences, and there was a deep emotional bond between them.
Adventure is also a big theme. They go on all sorts of adventures in the wizarding world, and fanfiction writers like to continue that. Maybe they go on a new quest to find a lost magical artifact or solve a mystery that was left unsolved in the original books. It gives the characters a chance to show their skills and grow even more.
There are also fanfictions where the news of Hermione and Ron's pregnancy spreads across the wizarding world. Their friends from Hogwarts are excited and plan a big celebration. However, they also face some challenges. For example, there could be some dark wizards who might see this as an opportunity to target them, so they have to take extra precautions to protect their unborn child.
One possible fanfiction could be where Hermione gets jealous when Ron starts spending a lot of time with a new female student in Hogwarts. She starts acting out in class and Ron doesn't understand why at first. Then, Harry has to step in and make Ron realize that Hermione might be feeling left out. This could lead to a big argument between Ron and Hermione which Harry tries to mediate.
It also shows the freedom and diversity in fanfiction. While it might not be in line with the original spirit, it allows for different creative ideas to be explored. However, it can cause some division within the fan community between those who support this new take and those who firmly oppose any deviation from the original relationships.