Well, in many fanfictions, at the start, there's often confusion and secrecy. Maybe Harry discovers the truth in a dramatic way, like finding an old letter. Then, as they get to know each other better, they form a bond. Esme might start to protect Harry like a mother would, and Harry begins to see her as a real mother figure, sharing his problems and joys with her.
In the 'harry is esme's son fanfiction', their relationship development is an interesting journey. At first, there could be a sense of unease for Harry. However, Esme's gentle and caring demeanor starts to draw him in. As the story progresses, they could engage in heart - to - heart conversations. For example, Esme might share stories from her past to make Harry understand their connection better. Harry, in turn, starts to rely on her for emotional support, and this mutual dependence cements their mother - son relationship in the fanfiction.
Typically, in such a fanfiction, their relationship development can be quite complex. It could start with Harry being skeptical about this new connection. But Esme, with her kind nature, gradually breaks down his barriers. They might have shared experiences, like facing a common enemy. Through these, their relationship deepens, with Harry growing to trust and love Esme as his mother, and Esme feeling a strong maternal love for Harry.