Another theme is friendship or romance. Many fanfics explore the relationship between the female character and Peter Quill. It could start as a friendship based on mutual respect for each other's skills, and then develop into something more romantic as they share more experiences.
One great female Peter Quill fanfic is 'Starlord's New Ally'. It shows a female character joining forces with Peter Quill on his adventures. The story has great character development for both.
He might meet his old friends from before he left Earth. People he used to hang out with, like schoolmates or neighbors. They could be shocked to see him after all this time and how much he has changed.
There's a fanfic where child Peter Quill discovers an ancient artifact on Earth. In this story, he starts to show his natural curiosity and his penchant for adventure even at a young age. It's really interesting as it also weaves in some of the alien cultures that he would later encounter in a very subtle way.
There could be a fanfiction where a female version of Peter Quill exists in an alternate universe. She has all of his charm and bravado but with a unique feminine twist. This fanfiction could explore how she rises to become a leader in her own right within the Ravagers, defying the expectations of those around her.
One possible plot could be that they discover Gamora is pregnant while on a mission. They then have to quickly find a safe place to hide and prepare for the baby. Along the way, they encounter old enemies who now see Gamora's unborn child as a valuable asset.
Peter Quill's origin story begins on Earth. He had a difficult childhood as his mother passed away when he was young. After being abducted by Ravagers, he was thrown into a world full of strange and diverse alien races. This experience shaped him into the adventurous and somewhat roguish Star - Lord we know. He learned to survive in the harsh and unforgiving space environment, using his wits and the few Earth - based items he had, like his Walkman, which also held sentimental value as it was related to his mother.
Peter Quill and Mantis aren't siblings in the comic world. There's no established connection of that kind. They have their own unique roles and arcs that don't involve being related by blood.