Well, in some fanfictions, the story could focus on the father's role. If it's Jace, for example, he might be overprotective. There could also be a plot where Clary discovers new powers or abilities that are related to her pregnancy, like some kind of enhanced intuition for protecting the unborn child.
Well, perhaps there's a plot where they discover some ancient prophecy related to their baby during the pregnancy. And they spend the whole time trying to figure out what it means and how to ensure their child's safety according to the prophecy. They might seek help from different factions in their world, like the Shadowhunters or Downworlders.
One popular storyline could be how they deal with the challenges of being young and expecting in the dangerous world of Shadowhunters. They might have to face threats from demons while also preparing for the baby.
Obviously Clary herself is the central character. Jace is also very often involved as he is Clary's love interest. Alec and Isabelle Lightwood might also play important roles. They could be the ones helping Clary through her pregnancy, giving her advice or protecting her from any threats.
Alec would likely become more protective. His natural instinct to safeguard would intensify not just for Clary but also for their unborn child. He'd be constantly on guard against any potential threats.
One possible plotline could be Clary finding out about Jace's cheating and feeling extremely betrayed. She might then decide to leave him and try to build a new life for herself and her unborn child.
There is a fanfiction called 'Alec's Perspective on Clary'. This one is interesting as it gives insights into Alec's thoughts about Clary. It shows how his initial wariness turns into a sort of begrudging respect and then friendship as they face different challenges in the Shadowhunter world.
Another scenario could be that Clary has to choose between her duties as a Shadowhunter and her love for Simon. She loves the Shadowhunter world and wants to protect it, but she also loves Simon deeply. In the fanfic, she might find a way to balance both, which is a great exploration of their love.
One interesting plotline could be Alec getting hurt while on a solo mission. He might be underestimated by the enemy, but then he ends up in a really bad state. This forces the other characters to reevaluate how they send out Shadowhunters alone. It also gives a chance for his relationship with Magnus to be tested as Magnus tries to help him recover both physically and mentally.
One memorable moment could be the first kiss. In many fanfictions, it's described as a passionate and long - awaited moment. It might happen in a dangerous situation, like right after they've fought off some demons. The intensity of the moment, with their emotions running high, makes it really stand out.
A plot could revolve around their family. They might decide to adopt a young Shadowhunter in need. This would bring out their parental instincts and also show how they support each other in raising the child. They could also face opposition from some in the Shadowhunter community who don't think they are suitable parents, but they prove them wrong through their love and determination.