It can start with a common goal. For example, they both want to stop a certain group of criminals. Working towards this goal makes them interact more, leading to the development of their relationship.
By having them face challenges together. Let's say they are trapped in a strange dimension. In this difficult situation, they have to rely on each other. Robin might use his strategic mind, and Blackfire her powers. This mutual reliance can strengthen their connection. They could start to understand each other's motives and fears better, and as a result, their relationship grows. They might go from distrusting each other to becoming true friends or even something more.
Dialogue is key. In fanfiction, creating conversations between them that gradually reveal their true selves can develop their relationship. Maybe Blackfire shares her past experiences with Robin, which makes Robin see her in a new light. And Robin can talk about his own dreams and values, which in turn interests Blackfire. Through these exchanges, their relationship can evolve from a simple acquaintance to a deep and meaningful one.
Another way is by introducing a third party that threatens their relationship. For example, a new hero comes in who tries to take Robin under their wing. Nightwing then has to prove why he is the better mentor. This would create some drama and further develop their relationship as they work through this new situation.
Their relationship can be developed through shared adventures. For example, when facing a really tough enemy, Luffy's determination to protect Robin and Robin's trust in Luffy's strength can bring them closer. Each time Luffy saves Robin from danger, it deepens her respect and loyalty to him.
Another way is through shared experiences. Let's say they both get caught in a time - travel anomaly. They have to rely on each other to find their way back to their own time. During this adventure, they learn about each other's fears, hopes, and dreams. This shared experience could be the catalyst for a deeper connection between them, whether it's a friendship based on mutual understanding or a more complex relationship.
Another way is through shared trauma. If they face a really tough villain who almost kills one of them, they can come out of it with a deeper understanding and a stronger father - son relationship. They can have heart - to - heart talks about their fears and insecurities during the recovery process.
They can develop their relationship through shared hobbies. For example, if they both like reading, they could start a book club together at school. This would give them time to talk and get to know each other on a deeper level.
The relationship could also develop because of a misunderstanding. Maybe Blackfire is trying to help the Teen Titans in her own way, but Robin misinterprets her actions as being sneaky. This causes a rift between them at first. But as they work through the misunderstanding, they learn more about each other. Blackfire explains her motives, and Robin realizes he was wrong. This new understanding could lead to a closer bond, with Robin seeing Blackfire in a new light and starting to develop feelings for her.
Their relationship can be developed through shared secrets. For instance, they could both discover something about the League that they're not supposed to know. Keeping this secret between them would bring them closer.
Their relationship can be developed through shared experiences. For example, going through a tough battle side by side where they both have to save each other's lives. This would create a bond of trust between them.
They could start by respecting each other's skills. Robin admires Wonder Woman's strength and she respects his intelligence. They could have shared training sessions where they exchange tips and grow closer. For example, Robin teaches Wonder Woman some new ways to analyze battle strategies quickly.
First, they could start with a mutual interest in knowledge. Robin loves to study history, and if the OC has some special knowledge or a thirst for knowledge as well, that can be a starting point. For example, if the OC discovers a new type of Poneglyph and brings it to Robin's attention.