Zuko would be very supportive. He has come a long way in his character development and would see this as a new chapter for the group. He might offer resources from the Fire Nation to help with the pregnancy, like the best healers or special herbs that could be beneficial for Katara during this time.
Sokka would probably be overprotective. He's always been protective of Katara, and now with her being pregnant, he would be constantly worried about her safety and the well - being of the baby. He might offer all kinds of advice, some of which might be a bit silly but well - intentioned.
Aang would be very happy and supportive. He has always been a friend to both Zuko and Katara, and he would see their union and the upcoming baby as a positive step towards more harmony in the world. Sokka might be a bit overprotective at first, especially towards Katara. But eventually, he would come around and be excited about being an uncle. Toph would probably make some sarcastic but also very endearing comments about the whole situation.
Toph would be blunt about it. She might tell both Aang and Katara that they're being stupid if she thinks the break - up is over something silly. But if it's a more serious issue, she'd support them in her own way. She might offer a place for Katara to stay if she needs to get away from Aang, or she might give Aang some tough - love advice on how to handle the situation.
Katara could be heartbroken. She might initially be in denial, not believing that Aang has actually left. Then she could become angry, feeling betrayed by Aang's sudden departure.
Some of their friends from the Fire Nation, like Mai, could be hesitant. She might worry about the implications for the Fire Nation's future and Zuko's role as a leader. However, as time passes and she sees how much Zuko loves Katara and their unborn child, she becomes more accepting. On the other hand, the Water Tribe elders could have mixed reactions. Some might see it as a good sign of unity, while others might be concerned about cultural differences.
Aang might go into a deep state of depression. He has always been an emotional character, and having his heart broken by Katara, someone he loves deeply, could send him into a downward spiral. He might isolate himself from his friends and stop practicing his bending for a while.
The Fire Nation, which has now become more of an ally, would also see this as a positive thing. Zuko, being Aang's friend, would be happy for them. He would see it as a sign of peace and unity among the different nations. The Fire Nation people might send some precious gifts as a sign of their respect for the union, as they know how important the Avatar and Katara are to the new world order.
Sokka would be protective of his sister. He would probably start by trying to negotiate with Zuko's side to call off the marriage. If that doesn't work, he might come up with a plan to rescue Katara, perhaps enlisting the help of their other friends and allies.
Since Katara is a strong - willed and empathetic person, the baby could inherit her compassion. They would be the type to help others in need, perhaps using their bending abilities to do so. Their personality might also be a blend of both parents' determination, making them a force to be reckoned with when they grow up.
Their relationship could deepen as they share in the joys and sorrows of rebuilding the world. They've been through a lot during the war, and now they can truly rely on each other. They might become even closer friends at first, with a mutual respect for each other's abilities growing stronger.
Some fans might depict the baby with light blue eyes like Katara and light brown hair like Aang. Others could give the baby a unique skin tone that is a blend of the Air Nomad and Water Tribe complexions. The baby might also be drawn with a small ponytail like Aang's, or with Katara's hair accessories.