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.
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.
Love and support are very common themes. Since the situation is quite unique, showing how Sirius and Remus support each other through the pregnancy is often a central part. Another theme is acceptance, as they have to accept this new reality in their relationship.
Well, often there's a strong theme of family and connection. Since Sirius is like a father figure to Harry in the original series, in mpreg fics it can explore a new level of that bond through the pregnancy aspect. Another theme could be protection, as both characters would be very protective of the new life.
The theme of freedom is quite important too. Sirius was locked up in Azkaban for a long time, and when he escaped, he was fighting for his freedom. Fanfictions often expand on this, showing his journey to fully regain his freedom and his place in the wizarding world, while also dealing with the prejudice against him because of his supposed crimes.
The theme of redemption also shows up. Since Sirius had a somewhat 'tainted' reputation in the eyes of the Black family, some fanfictions explore if Orion could have played a role in his redemption or if Sirius could have redeemed the family name in Orion's eyes.
One common theme is family. Since Sirius comes from the Black family, stories often explore how his child is related to the family's complex history, traditions, and dark secrets.
One common theme is family heritage. Since the Blacks are an old pure - blood family, many fanfictions explore how Sirius Black's mother dealt with the family's traditions and expectations. Another theme is the mother - son relationship. Given Sirius's rebellious nature, how his mother reacted to it and how it affected their relationship is often explored.
The theme of loss is also prevalent. Whether it's the loss of his freedom, his friends, or his chance at a normal life. For example, in some fanfictions, his relationship with James Potter is explored, and how his death was a huge loss for Sirius, adding to his overall sadness.
One common theme is the fight for justice. Sirius was wrongly arrested, so many fanfictions focus on him trying to prove his innocence. Another theme is the struggle against the Dementors. In Azkaban, the Dementors are a constant threat, and fanfictions often show how Sirius battles the despair they bring. There's also the theme of loyalty, as his friends either believe in him or start to doubt him, which creates interesting storylines.
Themes of secrecy and discovery are also common. In the wizarding world, there could be reasons to keep the pregnancy a secret, and then the story might revolve around how that secret is either kept or eventually discovered. Additionally, themes of love and sacrifice might play a big part, as Sirius might have to make sacrifices for the well - being of the pregnant situation and the future of the child.