Yes, there are some hints of a special relationship between them. In the movies and comics, they share a unique bond. Hulk seems to have a certain level of protectiveness towards Black Widow, and she is one of the few who can somewhat reach out to the Hulk within Bruce Banner.
The separation of the Hulk and Banner varies in Marvel comics. Sometimes, external forces or internal conflicts cause them to split, but it's not a consistent occurrence throughout all comics.
In the Marvel realm, the idea of a Black Widow and Hulk love story is an interesting concept. Their relationship was nuanced. Black Widow's ability to interact with Hulk on a different level than most was a sign of something special. While it may not have been a full - blown love affair like some other superhero pairs, there were elements of mutual respect, trust, and perhaps a bit of unspoken attraction. This was shown in their interactions where Black Widow could reach out to the Hulk in ways others couldn't.
No. Marvel Comics is a family - friendly entertainment medium for the most part and does not include such inappropriate content related to sexual stories about its characters like Hulk.
In the Marvel universe, Hulk and Black Widow had a complex relationship, but it wasn't really a typical 'love story' in the romantic sense. They had a connection based on their shared experiences as Avengers. However, the idea of a full - fledged love story between them was cut short mainly because of the nature of Hulk's character. He is often more of a brute force, and his transformations made a stable relationship difficult. Also, Black Widow had her own set of storylines and relationships that took precedence in different story arcs.
The main character is obviously the Hulk. And of course, Bruce Banner, who is the Hulk's alter ego. There may also be characters like Betty Ross, who has a complex relationship with both Bruce and the Hulk.
One common theme is the idea of the Hulk finding acceptance among the female characters. Since he's often seen as an outcast, in these fanfictions, the female characters welcome him into their group. Another theme is teamwork. They all have to work together to face various villains or challenges in the Marvel universe.