One common theme is friendship. It shows how deep and meaningful a friendship can be between Harry and Tonks. Another theme could be healing, as Harry helps Tonks heal from emotional wounds.
Well, in some fanfictions, Harry might comfort Tonks by simply being there for her. He could listen to her problems, like if she's worried about her family or the situation in the wizarding world. Just his presence can be a source of comfort.
One common theme is redemption. Draco often has to atone for his past actions towards Harry, and his act of comforting is a part of that redemption arc. It shows his growth from a bully to someone who can be empathetic.
The theme of forgiveness also often appears. Harry, having known Snape's past actions that were not always in his favor, has to come to terms with forgiving Snape in order to accept his comfort. And Snape, in turn, has to forgive himself for his past misdeeds. Another theme could be the power of connection. Despite their differences, they find a connection through shared pain or a common goal, and this connection is what allows Snape to comfort Harry.
In many of these fanfictions, the theme of self - discovery is intertwined with Harry's comfort. Ginny might be struggling with her identity, especially as she grows from a young girl into a woman in the wizarding world. Harry, with his own journey of self - discovery, is able to guide and comfort her. He might encourage her to pursue her dreams, whether it's in Quidditch or in her magical studies, and assure her that she is capable and strong, which gives her the confidence she needs.
One common theme is friendship. It shows how their bond can be a source of comfort. George is often depicted as being very empathetic towards Harry.
One common theme is the struggle against prejudice. Since they are an unusual couple in the wizarding world, they often face judgment from others.
One common theme is the idea of finding love in the midst of chaos. Given the war - torn world they live in, their love can be a haven. Another is the exploration of Tonks' unique abilities as a Metamorphmagus and how that adds an interesting dynamic to their relationship. For example, she might change her appearance to make Harry laugh or to show her different moods related to their relationship.
A major theme is the exploration of their unique magical abilities. Tonks' Metamorphmagus ability and Harry's connection to Voldemort are often used as plot devices. For example, some fanfictions have Tonks using her ability to help Harry in some way. Also, the theme of sacrifice is common. Since both are in the fight against the Dark side, they may have to sacrifice things for the greater good in these stories.
The theme of self - discovery is also present. Through the betrothal, Harry and Tonks learn more about themselves. They discover new aspects of their personalities, their likes and dislikes, and how they can grow as individuals while being in this unique relationship. This is often shown through their interactions with each other and how they face challenges together.
Often, there could be a theme related to Tonks' identity as a metamorphmagus and how that affects her pregnancy. Maybe she has to be careful not to accidentally change her form in a way that could harm the baby. Also, the theme of protecting the unborn child from the various threats in the wizarding world, like dark wizards or magical creatures, could be present in these fanfictions.