Often, they explore different relationship dynamics. With a female John, the emotional exchanges can be more nuanced. For example, the way she might communicate her thoughts and feelings to Sherlock could be different from a male John.
The fanfic could also focus on the challenges they face in society as a non - traditional family. John and Sherlock might face discrimination or skepticism from others when they try to adopt Harry. However, they persevere because of their love for Harry and each other. This could show how their strong bond helps them overcome external difficulties and build a loving home for Harry.
There's also 'John and Sherlock: The New Case'. This fanfic delves deep into the psychological aspects of both characters as they face a particularly complex case. It's really interesting how the writer explores their thought processes and how they interact with each other during the investigation.
Fanfiction.net is also a good place. There are many John Sherlock fanfics there. However, the quality may vary, so you might need to read the reviews or summaries before diving in. Some authors on this site have been writing John Sherlock fanfic for years and have a loyal following.
The fanfic could explore the dynamic changes in their relationships. Sherlock, who is usually aloof, might become more empathetic through the process of adopting Harry. John, on the other hand, would be the pillar of support for both Sherlock and Harry. Maybe Harry has some health issues that require Sherlock's deductive skills and John's medical knowledge to deal with, and this brings them closer as a family unit.
One common theme is friendship. Their relationship starts as a rather odd friendship between a brilliant detective and an ex - military doctor. Many fanfics explore how they grow to rely on each other more and more.
John might be a bit defensive at first. He's always been a bit more cautious about their relationship compared to Sherlock. He could try to downplay it in front of the Yarders, saying it's not as serious as it seems.
One popular one is 'The Great Game of Love' which beautifully explores Sherlock's internal struggle with his feelings for John. It has great character development.
One common theme is the exploration of their unspoken feelings. In many fanfics, Sherlock and John have deep emotions for each other that they struggle to express. Another theme is the idea of loyalty and how it plays out in their relationship. They are extremely loyal to each other, and this often gets tested in different scenarios in the fanfics.