Yes, he could be. Imagine Peter seeing Morgan as this new addition to Tony's life. Morgan might have a more 'normal' family relationship with Tony compared to Peter. Peter has his own insecurities and superhero life to deal with. If in the fanfic, Morgan is presented as having an easy and close bond with Tony, Peter might feel jealous as he's constantly struggling to fit into Tony's world while also handling his own.
One possible reason could be that Morgan gets more attention from Tony Stark. Peter Parker sees Tony as a mentor and father figure, and if Morgan is getting all the love and focus from Tony, it might make Peter jealous. For example, if Tony is spending more time teaching Morgan new things or just being with her while Peter feels left out.
His relationship with Morgan herself could also be affected. He might not be as kind to her as he should be. Instead of seeing her as a little girl who just happens to be in a situation where she gets a lot of attention, he could start to resent her, which would make their interactions awkward and uncomfortable.
Peter could be a character with some heroic or special qualities. He might be a young man with a big heart. Morgan could be a young girl, perhaps a student at the school. They could have a special bond, like an older brother - like figure (Peter) and a younger sister - like figure (Morgan).
One common theme is family. Since they are related in the source material, fanfictions often explore their family bond, whether it's a protective older - younger sibling relationship or just a strong family connection.
One great 'Morgan and Peter Parker fanfiction' is 'The Unlikely Bond'. It beautifully explores their relationship in a post - Endgame world. The story focuses on how Morgan, with her Stark - like intelligence, helps Peter with his scientific projects at school. Another good one is 'Morgan's Protector'. In this, Peter takes on the role of protecting Morgan from threats that emerge due to her connection to Stark Industries. There's also 'A New Friendship' which shows how they gradually become friends and support each other through their respective traumas.
In many fanfictions, Peter might feel replaced by Morgan because Morgan is Tony Stark's biological child. However, it's important to note that Peter also had a special bond with Tony. Maybe the new focus on Morgan in the post - Endgame world makes Peter seem sidelined in some stories. But this can also be a chance for character growth for Peter, as he learns to find his own place.
For a 'Morgan and Peter Parker fanfiction' to be good, it should explore emotions well. For instance, Peter's guilt over Tony's death and how Morgan might help him deal with it, or Morgan's feelings of growing up without her father. The pacing of the story is important. It shouldn't be too rushed or too slow. A slow - burn story that gradually builds their relationship can be really engaging. And the fanfiction should also introduce some new elements or twists. Maybe a new villain who targets them because of their connection to Stark, which would make the story more exciting.
Often, it's shown through Peter's internal monologues. He might think about how Morgan gets to have a normal family life with Tony while he has to hide his identity and fight crime. For example, he could be seeing Morgan have a simple dinner with Tony and feel a pang of jealousy because he rarely gets such a normal moment with Tony.