Well, I think in their married life, they would wake up early. Jace would probably be the first one up, making coffee for both of them. Then they'd get dressed in their Shadowhunter gear. During the day, they might be apart on different missions sometimes. But when they are together, they would hold hands and walk around the Institute, checking on the new recruits. At night, they would go to bed early, with Jace holding Clary close, protecting her even in sleep.
They communicate openly. Jace and Clary have been through a lot together before getting married, so they know the importance of talking things out. If there's a conflict, they would sit down and listen to each other's side of the story without interrupting.
One common theme is the adjustment to their new life together. They have to deal with the changes that come with being married and expecting a baby, like setting up a home. Another theme is the reactions of their friends and family in the fanfic world. Some fics might focus on how their family supports or maybe even opposes their situation at first.
The relationship would evolve significantly. Before the baby, they were mainly focused on their own adventures and relationship. But now, they are parents. They would need to support each other in different ways. For instance, Jace might be more protective of Clary and the baby. Clary would be more nurturing, and they would both have to learn to balance their duties as Shadowhunters with their new family life.
Their relationship would become more centered around the baby. They would have to make decisions together for the sake of their child, which would strengthen their bond.
It would change in many ways. They would go from being carefree high school sweethearts to having a lot of responsibilities. There would be more arguments as the stress of the situation builds up. But at the same time, they would also have deeper moments of love and understanding as they face this huge life change together. Jace might become more overprotective of Clary, and Clary would need Jace's support both emotionally and physically.
Clary might react with a sense of numbness at first. She's pregnant, which is a huge life change on its own, and then to find out Jace has cheated. She could withdraw into herself, not really knowing how to handle it. As time passes, she'll likely start to feel a deep sadness. She might cry a lot and feel like she's lost not only her relationship but also the future she had envisioned with Jace. However, her pregnancy could also give her the strength to be more independent and start thinking about building a new life for herself and the baby.
Well, it could be a wedding on top of a floating island. This island is only accessible to Shadowhunters. The whole place is decorated with runes that glow softly. Jace and Clary would have a simple yet elegant ceremony. Jace would hold Clary's hand tightly as they say their vows. And after the ceremony, they would have a celebration with all kinds of Shadowhunter delicacies and music that fills the air, while looking out at the beautiful view of the clouds and the world below.
Their friends are overjoyed. Simon, for one, is super excited and gives a really funny and heartfelt speech at the wedding. Isabelle is happy and helps Clary with all the wedding preparations, choosing the perfect dress and accessories. Alec is proud of Jace and is glad to see his brother find true love. The other Shadowhunters at the Institute also celebrate with them, seeing their marriage as a sign of hope and love in the often - dark world of Shadowhunting.
Jace will probably face a lot of guilt. His cheating not only hurt Clary but also has implications for the unborn child. He might find himself ostracized by their friends who side with Clary. Also, his reputation within their community in the fanfiction world could be severely damaged. If he realizes his mistake and wants to make amends, he'll have a long and difficult road ahead to earn Clary's forgiveness and trust again.
These fanfictions usually build on the existing relationship dynamics from the original source material. They might expand on the challenges that Jace and Clary face as a couple, like dealing with the secrets in their world or the opposition from other characters. And the 'lemon' parts are written to add a bit of spice and heat to their relationship portrayal.