The plot could start with Vegeta's sister being sent on a mission to Earth. Goku, being the protector of Earth, initially sees her as a threat. But as they interact more, they realize they have a lot in common. They start to explore their feelings for each other secretly. However, Vegeta discovers their relationship and is furious. He challenges Goku to a fight, thinking Goku has betrayed him. In the end, Goku and Vegeta's sister have to prove to Vegeta that their love is real and that it won't harm their relationship as comrades.
I'm not sure of a specific 'Goku x Vegeta's sister fanfic' to recommend. You could try searching on popular fanfic websites like Archive of Our Own or FanFiction.net. They have a large collection of Dragon Ball related fanfics and you might be able to find what you're looking for there.
One common theme is the exploration of forbidden love. Since Vegeta's sister and Goku are from different sides in a way, their relationship goes against the norm. Another theme is the power - up journey. They often train together and become stronger while dealing with their feelings.
One common theme is rivalry - turned - friendship. Their long - standing rivalry in the original series is often explored in fanfics as a starting point that then evolves into a deeper connection.
Well, in a 'Vegeta x Goku' fanfic, interesting elements often include new power - up scenarios for both of them. For example, they could discover a new form together while training. Also, when the fanfic delves into their personal lives and how they interact outside of fighting, like Vegeta's family life and Goku's simple - minded yet pure hearted nature, it becomes really interesting. It's about seeing these two iconic characters in a different light and exploring their relationship from different angles.
One possible analysis could be that it often explores the dynamic between two powerful and complex characters. Goku Black, with his menacing and somewhat twisted nature, and Vegeta, the proud Saiyan prince. In fanfics, their interactions can range from intense battles to unexpected alliances. Maybe it delves into how Vegeta would react to Goku Black's presence, given their different ideologies and power levels.
A lot of 'dbz goku x vegeta fanfic' has the theme of redemption. Vegeta, in particular, has a complex past, and in these fanfics, his relationship with Goku can be a part of his path to redemption. Also, the theme of family is present as they both have families and their interactions can be influenced by their family values. There's also the overarching theme of the Saiyan pride that they both carry and how it affects their relationship.
Many fanfics have a plot where Goku Black challenges Vegeta's place as the second - strongest Saiyan. This leads to a series of battles and power - up moments for both characters. There could also be a plot where Goku Black infiltrates Vegeta's family life, causing chaos and forcing Vegeta to not only protect his family but also prove his worth as a fighter. And sometimes, the plot focuses on the power struggle within the Saiyan race, with Goku Black representing a new and dangerous element to Vegeta's understanding of Saiyan power.
It often starts with a shock or surprise at the mpreg situation. Then, they gradually learn to rely on each other more. For example, Vegeta might start to show a more caring side that he usually hides, and Goku might become more responsible. They'll have to communicate more, sharing their fears and hopes about the future with the baby.
A plot might involve Goku accidentally stumbling into Zeno's realm. Zeno, who has only seen beings either fear or revere him, is amused by Goku's lack of fear and his eagerness to spar. So, they start a friendly sparring match that has the potential to either create chaos in the multiverse if they go all out or lead to a new understanding between the two most powerful beings in the Dragon Ball universe.
One possible plot could be a story of Goku and Android 21 teaming up against a new and powerful enemy. They start off as reluctant allies. Goku is initially wary of Android 21 due to her being an android, but as they face challenges together, they begin to understand and respect each other's powers. They could learn new techniques from one another and in the end, become friends. This would be a great way to show their growth and the power of friendship across different species in the Dragon Ball universe.