Often, Harry and Hermione have to fend for themselves without Ron at first. They might feel betrayed and angry, but they also realize they need to be stronger. Then, they start to uncover the real reasons behind Ron's betrayal. Maybe they find out that Ron was being controlled or manipulated, and they try to save him from the dark side he has fallen into.
In some fanfictions, Harry and Hermione form new alliances with other characters. They could team up with Neville or Luna, for instance. Meanwhile, Ron might be working with the bad guys, but he gradually starts to have doubts about his actions as he sees the true nature of those he has joined. Eventually, there could be a big confrontation where Ron has to choose between his new 'allies' and his old friends.
In the world of fanfiction, this could be a very dark and interesting plot. It might be that Ron is influenced by some dark magic or some external force that makes him turn against his best friends. Maybe he's jealous of Harry's fame or feels overshadowed by Hermione's intelligence, leading to his betrayal.
Often, it ends with Hermione realizing her mistake. She might fight to make amends and try to save Harry from whatever danger she has put him in. For example, if she had handed him over to the bad guys, she could then turn against them and help Harry escape.
In fanfiction, their friendship often develops through shared challenges. For example, when they face a new dark magic threat in the wizarding world, they rely on each other more. Harry's leadership, Ron's humor in tough situations, and Hermione's knowledge combine to make them closer. They also develop their friendship by having deep conversations about their fears and hopes for the future. Maybe Harry shares his concerns about being the Chosen One, and Ron and Hermione support him wholeheartedly.
The development usually involves a lot of character growth. Ron has to grow up a bit more and become more responsible, which Hermione appreciates. Hermione, on the other hand, may learn to be more patient and less controlling. The marriage law acts as a catalyst for these changes. They might start off just trying to get through the legal requirements but end up truly caring for each other. For example, Ron might surprise Hermione with a small, thoughtful gesture, like cooking her favorite meal when she's had a tough day at work. These little things gradually build their relationship.
One plotline could be that Ron is lured by the promise of power. He betrays Hermione to join a dark wizard or group that offers him something he desires, like more status in the wizarding world. Another could be a love triangle gone wrong. If there's a new character who Ron fancies and this person convinces him that Hermione is standing in the way of their relationship, he might betray her.
Obviously, Ron and Hermione are the main characters as the baby's parents. Their personalities play a big role. Ron's humor and Hermione's intelligence are often passed on to the baby in different ways in the stories. Also, Harry Potter sometimes makes an appearance as the baby's godfather or just as a close family friend.
Hermione, on the other hand, could become more vulnerable yet also stronger. She has always been strong - willed, but this experience could break her down initially. However, as she copes with the miscarriage, she might find new depths to her strength. She could become more in tune with her emotions and learn to lean on Ron more, which is a change from her usually independent self. This new dynamic between them would reshape their characters as they support and grow with each other through this difficult time.
One possibility is that they might have a huge misunderstanding. Maybe they believe Harry has been hiding something dangerous or unethical from them. So in the fanfiction, they decide to abandon him for what they think is the greater good.
In many fanfictions, the relationships start off a bit rocky. For example, if Harry suddenly has a sibling, Ron and Hermione might be a bit cautious at first. But as they get to know each other, they start to bond. The siblings often bring out new sides of Harry, Ron and Hermione. They might become more protective or more relaxed. For instance, if Ron's sister gets along well with Hermione's sibling, Ron might feel even closer to Hermione.
Often, there's a period of sadness and confusion for both of them. Hermione might try to figure out what she did wrong and reach out to Harry. Meanwhile, Harry might start to realize that he misses her friendship. Then, there could be a reconciliation scene where they finally talk things out and their friendship is restored, stronger than before.