Often, there is also a theme of character growth. The experience of mpreg can be a catalyst for both Sirius and Severus to change and develop. They might become more empathetic, or they might have to learn to rely on each other in ways they never expected before. It's a way to take these well - known characters and put them in a situation that challenges and transforms them.
One common theme is redemption. Given their rocky pasts full of enmity, many fanfictions explore how they can redeem themselves in each other's eyes. For example, Sirius might realize that Severus wasn't all bad, and Severus might come to terms with the fact that Sirius had his own reasons for his actions. Another theme is friendship against all odds. They are two very different characters, but fanfictions often show how they can form a bond despite their differences. This can be really inspiring as it shows that even the most unlikely pairs can find common ground.
The exploration of their shared past is also a big theme. Since they were at Hogwarts together, fanfictions often go back to their school days to show how their relationship could have been different. And there's the theme of the power of love and friendship in unexpected places. Despite their initial hatred, they find a connection that goes beyond what they thought possible. It shows that love and friendship can bloom even in the most unlikely situations.
Love triangles are also somewhat common in Severus Snape and Sirius Black fanfiction. Sometimes it involves a love interest from the original series, like Lily Evans, and how their feelings for her, both past and present, impact their relationship with each other. It can add a whole new layer of drama and complexity to the story.
One common theme is the clash of personalities. Sirius is often seen as more carefree and rebellious, while Severus, even as a female, is likely to be portrayed as more reserved and intellectual. Their relationship in these fanfictions usually starts with some sort of conflict that they have to overcome.
In Severus Snape mpreg birth fanfiction, a recurring theme is the exploration of relationships. His relationship with the other characters, such as his friends or former enemies, may change. For instance, some might be more sympathetic than he expected, while others might shun him. Additionally, the theme of motherly/fatherly instincts in Snape is often explored, as he has to adapt to a role that is very different from his usual self.
Most official 'Harry Potter' - related platforms and communities do not encourage or support mpreg fanfiction as it goes against the established lore in many ways. It's better to focus on more traditional fanfiction themes that are more in line with the essence of the story, such as friendship, adventure, and magic within the wizarding world.
A prevalent theme is the exploration of relationships. His relationships with his friends, like Remus and James (in flashbacks or through memories), are re - examined. How they support or sometimes struggle to support him is a big part of these fanfictions. Also, the relationship with the potential father of the child (if it's part of the story) is often a central focus, full of drama, love, and sometimes conflict.
I'm sorry, I don't have specific fanfiction titles to recommend directly. However, you can try searching on fanfiction platforms like Archive of Our Own. They have a large collection of fan - created works, and you can use the search filters to look for stories involving Sirius Black and Severus Snape in the context you want.
Another theme is the adaptation to the new situation. They have to deal with the physical and emotional changes that come with the male pregnancy. For example, Lupin, being a werewolf, might have additional concerns about how his condition could affect the pregnancy, and Snape would use his potions knowledge to try and ease any difficulties.
One possible plotline could be a magical accident that results in an unexpected situation similar to mpreg, but rather than focusing on the physical aspect, it could be more about the emotional and social implications for Snape and Black within the wizarding community. How they deal with the stares, the rumors, and the support or lack thereof from their friends.