One possible plot twist could be that they get married in secret to avoid the Capitol's interference. Maybe they use their combined skills from the Hunger Games to create a new life away from the prying eyes of the Capitol. Another could be that one of them is forced into the marriage for political reasons, but then they actually fall in love during the process.
One plot twist could be that Gale discovers a long - lost relative who tries to stop the wedding because of some ancient family feud. Another could be that Katniss has a premonition on the wedding day that something bad will happen in the future if they go through with it, making her question the marriage at the last minute. Maybe there could also be a political plot twist where the Capitol tries to use their marriage as a tool for propaganda, but Gale and Katniss find out and have to decide whether to go along with it or fight against it.
Maybe there's a new threat in the form of a political faction that wants to undermine their relationship. They try to spread rumors that the baby isn't Peeta's or that Katniss is using him for power. This forces Katniss and Peeta to fight not only for their family but also for their reputations in the district.
One possible plot twist could be that the pregnancy is a result of some Capitol - engineered experiment. Maybe they were secretly given a fertility - enhancing drug during their time in the Games. This would add a whole new layer of danger and mystery to the story as they try to figure out what the Capitol's motives are and how to protect their unborn child.
One possible plot could be that in an alternate universe where the Hunger Games have a different set of rules. Katniss and Cato are forced into an unexpected alliance due to some strange Capitol decree. As they spend time together, feelings develop in a very unexpected way and Katniss becomes pregnant. This would lead to a huge shift in their relationship dynamics and also their standing in their respective districts.
One possible plot could be that after the Games, Cato somehow survives and he has a change of heart. He realizes the horror of the Games and starts to see Katniss in a new light. They bond over their shared trauma and eventually fall in love and get married.
One possible plot twist could be that Sakura discovers Kakashi has a secret past she never knew about. Maybe he was involved in some kind of dangerous mission long ago that has consequences in the present. This could put a strain on their relationship as she tries to come to terms with this new information.
One possible plot twist could be that just before the wedding, Ayame discovers a long - lost relative who has some dark secrets about Kouga's family. This relative tries to stop the wedding by revealing these secrets to Ayame. Another could be that on the wedding day, an old enemy of Kouga shows up and challenges him to a fight, putting the wedding on hold. Or perhaps there is a misunderstanding where Ayame thinks Kouga has betrayed her trust in some way, like he made a deal with an enemy for the sake of the tribe but didn't tell her.
Maybe Hikari suddenly gets an amazing job opportunity in a far - off place. This would force them to decide between following Hikari's career dreams and staying in their current comfortable life. It could lead to some really emotional and tense moments in the fanfiction.
One possible plot twist could be a long - lost relative showing up at the wedding and revealing a family secret that threatens to stop the marriage. For example, if there's a feud in the family that was hidden from Heiji and Kazuha.
One possible plot twist could be that their marriage is part of a larger plan to infiltrate an enemy organization. They pretend to be a happily married couple but are actually gathering intel. Another could be that Neo's past catches up with her during the wedding, and they have to deal with old enemies trying to disrupt the celebration.