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.
Another theme is the growth of the relationship. The pregnancy can either strengthen or test the bond between Sirius and the OC. Sometimes it shows how they come closer together, learning about each other on a deeper level.
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.
One common theme is the exploration of their relationship in a new light. With the pregnancy, they have to reevaluate their feelings and commitment to each other.
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 the vulnerability of Sirius. Usually, he's portrayed as this strong, brave character, but when sick, he shows a different side. Another theme is the support from his friends and family. They often rally around him, highlighting the importance of those relationships.
One common theme is family conflict. Sirius rebels against the pure - blood mania and dark magic - associated ways of the Black family that Walburga represents. Another theme is the struggle for identity. Sirius is trying to be his own person away from the expectations set by his family with Walburga as a symbol of those family constraints.
One common theme is love. Often, the female character falls in love with Sirius Black, exploring the different aspects of romantic relationships in the wizarding world. For example, how they deal with the danger he's in and the secrecy required in their relationship.
One common theme is loyalty. Sirius was extremely loyal to his friends, and fanfictions often explore this aspect in different situations, like when he was in Azkaban but still held onto his love for James and his friends.
One common theme is unrequited love. Sirius might be jealous because he loves someone who doesn't seem to return his feelings in the same way. For example, he could be jealous of someone else getting closer to the person he has feelings for.
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.