Love and family would be a major theme. Zuko and Mai's love for each other is shown through their joint responsibility of raising their child. Another theme could be growth. They both grow as individuals as they learn to be parents.
The theme of adaptation is also likely. They have to adapt to having a new member in their family, new responsibilities, and a new dynamic in their relationship. This could involve adapting to sleepless nights, the baby's needs, and how it changes their daily lives.
Perhaps the fanfiction delves into the baby's unique abilities or characteristics. Since Zuko has a connection to the Fire Nation and Mai is a skilled fighter, the baby could inherit some extraordinary powers. It could show how they train the baby to control these powers while also giving it a normal childhood.
Zuko can be developed by exploring his role as a leader within the context of his marriage. He may struggle to balance his duties as Fire Lord with his time for Mai. This internal conflict can show his character's depth. He could also develop new bending techniques influenced by his love for Mai. As for Mai, she can develop by getting involved in more political matters, standing by Zuko's side and using her intelligence to influence decisions. She could also start to make more friends in the palace, which would change her somewhat solitary nature.
One common theme is the power dynamic. Ozai is a powerful figure in the Fire Nation, and how he wields that power over his baby son, Zuko, is often explored. For example, in many fanfictions, he starts to instill in Zuko the importance of strength and power from a very early age.
One common theme could be the growth and development of the baby in the context of mai and naru's relationship. For example, how they adjust to being parents and the challenges that come with it.
Zuko's personality could be shown as more tender and caring than ever. He might be constantly worried about Mai's well - being and that of the baby. His sense of responsibility would be heightened. Mai, on the other hand, while still maintaining her dry sense of humor, would show a more vulnerable side. She may not be as openly emotional as Zuko but her actions, like making sure the nursery is safe, would show her love and care for the unborn child.
Mai could be jealous of Zuko in fanfiction if there are rumors about Zuko and another character. Just like in real life, rumors can spread like wildfire in fictional worlds too. If there are whispers in the Fire Nation palace about Zuko having a special connection with someone else, Mai would not take it lightly. Her jealous side would emerge as she tries to find out the truth and put an end to these rumors.
One possible scenario in such a fanfiction could be that Zuko is getting a lot of attention from other characters. Maybe he's being praised for his leadership skills or his newfound wisdom. Mai, being his girlfriend, might start to feel left out and jealous. For example, if Zuko is constantly in the company of a female character who admires him greatly, Mai could see this as a threat to their relationship. She might then start to act cold towards Zuko or become overly possessive to assert her claim on him.
One popular theme is the journey of Katara and Zuko raising their baby in a world that is still recovering from war. Their different cultures, Water Tribe and Fire Nation, can play a big part. For example, they might have to decide which cultural traditions to pass on to the baby. Another theme could be how their friends and family react to the new addition. Aang might be excited to have a new little friend, while some Fire Nation nobles could be skeptical or even hostile at first.
Well, the theme of family also often comes up. Zuko's family situation is complicated, and Mai is also affected by her family's expectations. Fanfics may explore how their relationship is influenced by their families. For example, how Zuko's relationship with his father affects his relationship with Mai. Also, the theme of growth is common. Both Zuko and Mai grow as characters in fanfics, learning more about themselves and each other.
Maybe a plot where Mai is kidnapped by enemies of the Fire Nation who want to use her to get to Zuko. Zuko then embarks on a dangerous rescue mission. Along the way, he realizes just how much Mai means to him. Or a story where Zuko and Mai are forced into an arranged marriage by Fire Nation politics. At first, they resist, but as they spend more time together, they start to develop real feelings for each other that go beyond the political arrangement.