Another theme is the power dynamics in their relationship. Tonks is a confident and strong witch, while Remus has his own insecurities. Fanfictions might explore how they balance this in their romantic relationship, especially during more intimate or 'lemon' scenes where they both have to be vulnerable with each other.
One common theme is their relationship. Writers often explore how Remus and Tonks got together, their initial attraction, and how they dealt with the challenges in their relationship, like Remus's self - doubt due to his werewolf condition.
One common theme is acceptance. Remus has to accept his own identity as a werewolf and Tonks has to accept the challenges that come with loving him. For example, in many fanfictions, Remus is initially hesitant about being with Tonks because of his condition.
One common theme is the fear and worry. Given Remus's condition as a werewolf, there's often concern about how it might affect the pregnancy or the child. Another theme could be the support system around them. Their friends in the wizarding world might play important roles in helping them through this time.
A major theme is the struggle with society's expectations. In the wizarding world, a werewolf like Remus is often stigmatized. Fanfictions often explore how Tonks and Remus deal with this. Also, the theme of redemption can be seen. Remus may see Tonks as a sort of redemption, a chance to have a normal life despite his affliction, while Tonks may see helping Remus as a way to redeem the unfairness of the world towards him.
Love against all odds is a very common theme. Given Remus' condition as a werewolf, they face a lot of opposition and prejudice. Fanfictions often explore how their love overcomes these difficulties.
A common theme could be the power of memories. Remus and Tonks might share their memories with Teddy, which would help him understand his heritage. Another theme could be the idea of second chances. They never got to be a proper family when they were alive, but in the fanfiction, they get a chance to start anew. And of course, the theme of magic is always there. They could use magic in creative ways to bond with Teddy, like creating magical family portraits or using spells to play games together.
Often, there can be themes of forbidden love. Given Remus' age and his position as a teacher - like figure in Harry's life in the original series, the idea of crossing that line can be a common theme.
One idea could be to focus on how they prepare for the baby's arrival. Maybe Remus is worried about his werewolf condition affecting the child, and Tonks has to constantly reassure him. They could start decorating the nursery with magical elements.
In fanfiction, their first encounter might be reimagined in various ways. It could be a chance encounter in Diagon Alley, where they bump into each other and there's an instant spark. Tonks' colorful hair and Remus' calm demeanor could create an interesting contrast from the start.
One common theme is loyalty. Their loyalty to each other is often explored deeply, as they've been through so much together. For example, in many fics, they stand by each other through difficult times at Hogwarts and later in life.