Another plot twist could be that Hermione is in some sort of self - imposed danger, like trying to solve a dangerous mystery on her own, and Draco has to step in to protect her without her knowledge at first. This changes the dynamic between them as she initially resists his help thinking he has ulterior motives.
A common plot twist is that Draco is secretly working against his family's wishes to protect Hermione. For example, his family might be part of a dark plot, but he chooses to side with Hermione instead. This adds an element of conflict and drama to the story.
Sometimes, there's a plot twist where Draco's protective actions lead to him being falsely accused of something. Maybe he's protecting Hermione from a dark wizard, but the wizarding community misinterprets his actions and thinks he's the bad guy. This then forces Hermione to defend Draco, strengthening their bond in the process.
One common plot twist is the revelation of a hidden family connection that makes them siblings. Another could be that they have to team up against a common enemy, like a dark wizard who is targeting their family. It might also be that Draco has to choose between his Slytherin friends and his new - found sister Hermione when there's a conflict between them.
A common plot twist is that Hermione actually has a hidden power or ability that she reveals during her captivity. For example, she might be able to use a type of magic that Draco and his associates didn't expect, which gives her an upper hand in the situation. This could lead to a change in their relationship dynamic, from captor - captive to something more like equals.
One common plot device is Draco flirting with other girls in front of Hermione. For example, he might shower another girl with compliments about her magical abilities which Hermione takes as a personal slight since she prides herself on her own skills. This immediately makes her jealous and sparks a series of events where she tries to show Draco that she doesn't care, but actually does.
One interesting plot twist could be that despite being siblings, they are sorted into different houses, and this causes a rift in their relationship initially. But as the story progresses, they find common ground in their magical abilities and family secrets.
Often, a plot twist could be the discovery that the baby is part of some ancient prophecy. This throws Draco and Hermione into a whole new set of challenges as they try to protect their child and fulfill the prophecy. Also, there might be a plot twist where Hermione's Muggle - born status causes problems. Some in the wizarding world might try to use the new baby as a way to target Hermione and her family again, despite her relationship with Draco.
A plot twist might be that the werewolf gene behaves differently during the pregnancy. Instead of the usual werewolf transformation problems, it gives Hermione or Draco the ability to communicate with other magical creatures in a unique way. Also, perhaps there is a prophecy related to the baby that no one knew about before the pregnancy. This could put Hermione and Draco in a difficult situation as they try to protect their unborn child from those who might want to use the prophecy for their own gain.
Another theme is the idea of hidden alliances. In many of these fanfics, the Slytherins form a secret group to protect Hermione. This adds an element of mystery and intrigue as they work behind the scenes to keep her safe from threats, both inside and outside Hogwarts.
Another scenario is during dangerous magical experiments or when they are exploring old, dangerous parts of Hogwarts. Draco, being more familiar with the darker aspects of magic in some cases, will be protective of Hermione who is always eager to learn and might not fully grasp the risks. In these fanfictions, he'll stop her from doing something too risky or help her out when things go wrong.
One common plot twist is that the child has some extraordinary magical power that neither Hermione nor Draco expected. Another is that the secret of the child's existence is threatened to be exposed by an old enemy. Sometimes, the child may turn out to be the key to solving a big mystery in the wizarding world.
Another theme is the changing of relationships. Their relationship, which was mostly adversarial in the books, takes a new turn. It can range from friendship to a more romantic relationship. For example, in many fanfics, the act of saving Hermione makes Draco realize his feelings for her that he had been suppressing.