Astrid might initially be in shock. She could just stand there, frozen, unable to believe that Hiccup is really gone. Her eyes wide open and her body trembling as she tries to process what has just happened.
Astrid may go into a state of denial at first. She would think that there must be some way to bring Hiccup back. So she might search for a cure if he was poisoned or a way to reverse time if it was some sort of magic - related death. But as time passes and she realizes there's no hope, she would be completely devastated. She might become withdrawn from others, spending most of her time in places that remind her of Hiccup, like the dragon stables or the cliffs where they used to fly together.
Hiccup would probably be very worried. He'd rush to her side immediately. He might start to check her injuries right away and call for help if needed.
It develops gradually. At first, they might be just friends who respect each other's skills. But as they go on more adventures together, they start to notice little things about each other. For example, Hiccup notices how Astrid is always the first to volunteer for dangerous tasks because of her bravery. And Astrid sees how Hiccup's intelligence always gets them out of tough situations.
Well, he might be initially shocked. He could stand there for a moment, his eyes wide open, trying to process the news. Then, he would probably break into a big smile and hug Astrid tightly, whispering words of joy and excitement.
Their friends are likely overjoyed at first. Fishlegs might be a bit of a nervous wreck, constantly worrying about Astrid's health and the well - being of the baby. He'd probably be reading every book he can find on dragon - rider pregnancies (if that's a thing in their world). Snotlout would probably make a bunch of inappropriate jokes at first, but deep down he's also excited. Ruffnut and Tuffnut would be their usual chaotic selves, but also show their support in their own unique ways, like bringing strange gifts they think the baby would like.
In some fanfictions, a heartbreaking scene might be when Hiccup sacrifices himself to save Astrid from a powerful enemy. He might push her out of harm's way just as a deadly attack is about to land on her, and then he takes the full brunt of it. The moment when Astrid realizes what he's done and rushes to his side, crying and begging him not to leave, would be extremely sad.
Hiccup might be very resistant at first. He's always been an independent thinker, so being forced into a marriage would go against his nature. He could try to find ways to escape the situation, like running away or finding loopholes in the marriage contract. But as he spends more time with Astrid, he might start to see her in a different light and become more accepting of the situation.
Their relationship might become more equal in some ways. As dragons, they are both facing a new and strange existence, so they have to rely on each other more. They might develop a new understanding of each other's strengths and weaknesses.
One possible fanfiction could be about how Hiccup and Astrid deal with the pregnancy. Hiccup might be overprotective, constantly worried about Astrid and the baby. Meanwhile, Astrid could be trying to keep up with her normal Viking duties while also preparing for motherhood. And the lemon element could be a symbol in the story, perhaps it's something Astrid craves during her pregnancy, leading to some humorous or heartwarming scenes between her and Hiccup as he tries to find the perfect lemon for her.
Astrid might also grow in her leadership skills. By taking the initiative to comfort Hiccup, she shows that she can be a source of support for others. This could translate into her being more confident in leading the group, as she realizes that being there for people is an important part of leadership.
The relationship between Hiccup and Astrid during her pregnancy would be a journey of growth. Hiccup would have to be more patient as Astrid's hormones might make her moody at times. Astrid would rely on Hiccup more, which could be a big change for her. They would also start making plans for their family, like where the baby will sleep and how they will raise it. Their love would transform from the passionate love of two young adventurers to a more profound, family - centered love. They might also have some cute moments, like Hiccup talking to the unborn baby at night, which would make Astrid feel even more loved.