I'm not aware of any such fanfic specifically. It's a very strange and unorthodox concept that goes against the established canon in the Harry Potter series. The original story clearly shows that James Potter is Harry's father.
If there was such a fanfic, it could explore some very different themes. The idea of Harry having Voldemort as a father might lead to a story where Harry is conflicted about his own nature. He might struggle with the dark side of himself more. The wizarding world's reaction to this revelation would also be interesting. Would they still see Harry as the hero? Or would they fear him because of his connection to Voldemort? There could be a lot of internal and external conflict in the story.
Yes, there are some fan fictions that explore a romantic relationship between Voldemort and Harry. However, this is a very unconventional and often controversial concept within the Harry Potter fandom, as Voldemort is the main antagonist and his actions are extremely evil in the original story.
Well, a common theme is often the exploration of the forbidden. Their relationship is not only unexpected but also goes against the norms of the original story. It also might involve the theme of transformation. Harry could potentially change Voldemort, and in turn, Voldemort could change Harry in ways that are not possible in the original plot. There could also be themes related to the blurring of the lines between good and evil as their relationship develops.
I'm not sure if there is such a specific fanfiction. Fanfiction can cover a vast range of ideas, but this one seems rather unorthodox considering the established lore in the Harry Potter series. However, the world of fanfiction is so large that it might exist somewhere in the depths of the internet.
There's a good chance that his friends like Ron and Hermione would also be main characters. They were always by his side in the original series and would probably play important roles in this fanfic as well, perhaps helping Harry explore and understand his new - found aspects of his magic.
The fanfic might focus on the relationships between Harry's future children. For example, they could have sibling rivalries or strong bonds of friendship. They might also have different personalities - one could be really outgoing and brave like Harry, while another could be more shy and studious. And they would all be growing up in a world that's still recovering from the war, so that could add a lot of depth to their stories.
Well, in these fanfics, a very common theme is the passing down of values. Harry has certain values from his own experiences, and in the fanfics, we often see how he tries to pass them on to Victoire. Another theme is the exploration of the wizarding world from a new perspective. Since Victoire is of a new generation, the fanfics can show different aspects of the wizarding world that were not explored in the original series. Also, the theme of self - discovery is quite prominent. As she grows, she discovers her own strengths, weaknesses, and what she truly wants in life, all while being Harry Potter's daughter.
It could be Hermione, if it's related to the Harry Potter universe. She is extremely brainy and would fit the description well. There might also be other new female characters who are introduced specifically in this fanfic to add more depth to the story.