Harry Potter would likely be one of the main characters. Since Ginny is his love interest in the original series, he would surely be affected by her marriage to Voldemort. He might be the one to try and rescue her or stop the marriage. Ron Weasley, Ginny's brother, would also be important. He would be outraged and would probably be part of any plan to oppose the union.
The Weasley family in general would be involved. Ginny, for instance, would be heartbroken seeing Harry on Voldemort's side. The family's loyalty to Harry would be put to the test, and they would be among the main characters as they try to either bring Harry back or fight against him if he goes too far with Voldemort.
Well, a plot could be that Voldemort has a change of heart after falling in love with Ginny. He starts to question his dark ways and Ginny, seeing this potential for good in him, decides to marry him in the hopes of fully turning him around. But this is met with great resistance from the wizarding community who see Voldemort as irredeemable. Ginny then has to fight not only for Voldemort's redemption but also for their relationship to be accepted.
Snape could also be a character in such a fanfic. His complex relationship with both Harry and Voldemort makes him an interesting addition. He might be in a difficult position, having to keep his cover as a double - agent while also trying to find a way to save Harry without revealing his true intentions to Voldemort.
Definitely the Weasley family. Molly and Arthur Weasley would be very much involved. Molly would be all excited about the wedding preparations, fussing over Ginny's dress and the food for the reception. Arthur would be there to offer his support and probably share some interesting wizarding stories. Ron and Hermione would also be there. Ron as Harry's best friend would be part of the pre - wedding jitters and celebrations. Hermione would be helping Ginny with all the details, like choosing the right flowers and making sure the wedding venue is decorated perfectly.
Snape could play a crucial role. Given his past with both Voldemort and his role at Hogwarts, he might be torn between his loyalty to Dumbledore's cause and his complex relationship with Harry. He could be the one who has to make a difficult decision when Harry starts to side with Voldemort. Additionally, Draco Malfoy could be involved. He might see Harry's change as an opportunity to gain more power within Voldemort's ranks, or he could be jealous of Harry's new - found position with the Dark Lord.
Harry Potter is central as the possessed. Voldemort is crucial as the possessor. Harry's friends are bound to be main characters. Hermione, with her intelligence, would be constantly observing Harry's strange behavior and coming up with theories. Ron, being Harry's loyal friend, would be by his side and ready to fight for him. Also, characters like Sirius Black, if he's still alive in the fanfiction's timeline, could be involved. He has a close connection to Harry and would surely want to help him get rid of Voldemort's control.
Well, in this sort of fanfiction, Ginny's motive could be a complex web of emotions. She might be under the influence of a dark spell. Or perhaps she has been misinformed about Harry's role and believes that by giving him to Voldemort, she's actually saving the wizarding world. It could also be a case of extreme jealousy, if the writer wants to explore a really twisted version of her character.
Yes, there might be some. However, it's a rather dark and unorthodox take on the Harry Potter universe. Some fanfictions like this explore extreme 'what - if' scenarios. But they often deviate greatly from the original spirit of the series.
Another plotline might be their family life. They could be shown starting a family early, and dealing with the joys and challenges of raising children in the wizarding world. For example, teaching their kids magic at home, or dealing with the chaos of a family full of young wizards.
There's a fanfic called 'Ginny and Harry: A Love Unhindered'. In this story, they start dating right after the defeat of Voldemort's minions in their final year at Hogwarts. Without the threat of Voldemort, they are able to fully explore their feelings for each other. They go on adventures across the wizarding world, from the beaches of Cornwall in the wizarding UK to the magical markets in Paris, just the two of them.