The main ethical issue is that it distorts the family - like bond they have. Aunt May is supposed to be a parental or at least a very close family figure to Peter. Turning that into a romantic or inappropriate relationship in fanfiction is not acceptable.
One great 'Peter Parker and Aunt May Fanfiction' is 'Aunt May's Wisdom'. It beautifully portrays the relationship between them. The story shows how Aunt May's words of wisdom always guide Peter in his life as Spider - Man. It's a heartwarming read that really delves into their bond.
I'm not aware of any such fanfic. Fanfics often cover a wide range of themes, but this combination seems rather unusual and might not be a common one in the mainstream Spider - Man fanfic world.
Well, it could be about Aunt May finding out some of Peter Parker's secret superhero adventures in a really comical way. Maybe Peter accidentally leaves his Spidey - suit out and Aunt May stumbles upon it. And their relationship could be explored further, like how she supports him in a more emotional and domestic setting within the fanfic.
A plot could be that Aunt May discovers Peter's newfangled gadget for his Spider - Man activities. She might be initially shocked but then becomes his biggest supporter in a very heart - felt way. The lemon part could come in as a bit of a comical misunderstanding. Say, Peter tries to explain the gadget and Aunt May misinterprets what he says, leading to some funny exchanges.
Peter might initially be in a state of shock. He could isolate himself from his friends and the world around him, constantly replaying memories of Aunt May in his head. He may also feel a great sense of guilt, thinking that he could have done more to protect her.
Another theme is protection. Aunt May wants to protect Peter from the dangers of being a superhero, and Peter wants to protect her from the threats that come his way because of his powers. For example, in many fanfictions, there are scenes where Peter tries to keep his superhero activities a secret from Aunt May to keep her safe.
The plot could be that Aunt May finds a mysterious lemon - colored object. Peter Parker, with his scientific mind and Spider - Man curiosity, tries to figure out what it is. As they explore, they discover that it has some kind of power related to Peter's Spider - Man abilities, and they have to keep it safe from villains who also want to use it for their own evil purposes.
Fanfiction involving such a relationship is often considered inappropriate as it goes against the traditional family - like relationship between Peter and Aunt May in the Spider - Man lore. It's not ethical, so I can't recommend any.
I'm not entirely sure if there is a specific 'Aunt May x Peter Parker pregnant' fanfiction. Fanfiction is a wild place where all sorts of ideas are explored. This particular concept is rather unorthodox given their relationship in the official stories. It might be a very niche piece of fanfiction if it exists at all. You could try using specific search terms on fanfiction platforms and see what comes up, but don't be too surprised if it's not a common theme.