It could be Ron Weasley. In many post - war fanfictions, Ron and Hermione get married and have children. Ron would be a great father, teaching the kid about wizarding traditions and Quidditch, while Hermione focuses on academics.
There could also be an original character as the father. Maybe a new wizard who comes to work at the Ministry of Magic. He and Hermione meet during a project and fall in love. This would give the fanfiction a chance to explore a new relationship dynamic and a fresh backstory for the kid.
One possible plot could be that Hermione's kid inherits her love for knowledge. Maybe the story shows the kid starting at Hogwarts and struggling to live up to the expectations of being Hermione Granger's child. They could face pressure from peers and teachers alike, but ultimately find their own path in the magical world, perhaps by specializing in a new area of magic that Hermione hadn't explored much.
There could also be some of Hermione's wizard friends like Harry and Ron. They might come to support Hermione during the reunion. And perhaps some of her extended family members from the wizarding world that she has just discovered. It could be an old aunt or uncle who has some interesting stories to tell. Maybe even some family members who were thought to be lost but have now returned. They would all add different dynamics to the family reunion, making it a really interesting event.
Perhaps it could be a new character. A mysterious wizard who comes into Hermione's life, and they fall in love and have a child. This would add an element of newness and mystery to the fanfiction, as the readers would get to learn about this new character and his relationship with Hermione.
Well, the kid might go on a journey to discover a new spell that was lost in time. Just like Hermione was always into books and knowledge, her kid could be on a quest to find ancient magical texts hidden in a secret library in Hogwarts.
It could be Ron. Since they have a relationship in the original story, it's a very likely option. Their relationship could be further developed as they face the new chapter of becoming parents together.
Well, it could symbolize a new beginning. Just like in real life, a new haircut can mark a change in a person. In fanfiction, Hermione getting a haircut might show that she's ready to break free from her old self, perhaps be more daring.
It could be a completely new character created for the fanfiction. Maybe a powerful witch who met Sirius during his time on the run. She could have been helping him and they fell in love, and then had a kid.
It could be an old flame that Bella had a brief relationship with. Maybe someone she met during a trip and then lost contact with until she found out she was pregnant.
One potential main antagonist could be a disgruntled professor. This professor might feel that Hermione is too much of a know - it - all and decides to deage her as a form of punishment. Or it could be a Death Eater who has infiltrated Hogwarts. They know that Hermione is a valuable asset to Dumbledore's side, so they deage her to weaken the opposition. The Death Eater could then use the deaged Hermione as a pawn in their evil plans.
In many fanfictions, Hermione Granger's family plays important roles. Her parents, who are dentists in the original series, might be depicted with more magical involvements in fan stories. For example, some fanfictions could explore how her parents adjust to the wizarding world after Hermione reveals her magical abilities to them more fully. This can add new dimensions to Hermione's character as well, as her family background and their relationship can shape her actions and decisions within the fan - created plots.