If such a fanfiction existed, it would be a very dark exploration of power, coercion, and the blurring of the lines between good and evil. Harry, who represents good, would be in a situation that goes against all his values. It would also raise questions about the nature of the child - would it inherit Voldemort's evil or could it be redeemed? And how would the wizarding world react to such an abomination? There would be a lot of political and social unrest in the story, as people would be divided on how to deal with this situation.
I'm not aware of such a fanfiction existing. The idea is rather dark and goes against the general themes of the original 'Harry Potter' series. The series is mainly about good vs. evil, and this concept seems very out of place.
There are indeed such fanfictions. Some explore really interesting concepts within this odd scenario. For example, in some stories, the forced marriage is a part of a dark plot by Voldemort to gain more power over the wizarding world through Harry. Others might focus on how Harry copes with this situation and tries to find a way out while also dealing with his complex feelings towards Voldemort. It's a very unique concept that can lead to some very creative storytelling.
Yes, there are some fanfictions with this rather strange premise. You can often find them on various fanfiction websites like Archive of Our Own (AO3). Just search for the relevant tags.
At first, Harry would be conflicted. He has always been against Voldemort, but now being forced to be with him would make him question his own beliefs. His character could become more cynical as he is exposed to Voldemort's dark world.
One possible implication is that Harry would gain a deep understanding of Voldemort's motives. He might see how Voldemort's past traumas, like being an orphan and feeling rejected at Hogwarts, led him down the dark path. This could make Harry more empathetic in a strange way, or it could also be a huge burden on him as he has to deal with all the dark and twisted thoughts that Voldemort had.
Perhaps Voldemort discovers a long - lost family secret of Harry's that gives him leverage. For example, he might find out that there is a curse on Harry's family that only he can break, but only if Harry joins him. Or Voldemort could be using some form of mind - control device that was created by an ancient dark wizard, which he uses on Harry to make him a part of his ranks.
One plotline could be that Voldemort wants to use the marriage to gain control over Harry's special powers. Another could be that it's part of a prophecy that neither of them can avoid. Or maybe it's a political move in the wizarding world to end the war between the two sides.
One possible plotline could be Harry trying to find a way to break the forced marriage bond while secretly gathering allies to fight Voldemort.
In fanfiction, the idea of Harry Potter and Voldemort as soulmates is an interesting concept. This could rewrite the entire dynamic of the story. It might suggest that their battles were not just about good vs. evil, but rather a struggle within a soulmate relationship. There could be a hidden harmony in their magic that only a soulmate bond could bring out. It could also make for a very different kind of character development for both of them, as they would have to come to terms with this unexpected connection.
If they were brothers in fanfiction, it would completely change the power dynamics. Harry, who was always the hero against Voldemort, would have to grapple with the fact that they are related. Snape's loyalty and his complex relationship with both Harry and Voldemort would be even more muddled. It could lead to a situation where they have to unite against a common enemy that is threatening their family legacy, or it could create a civil war within their 'family' as they have such different ideologies.