A werewolf could be an interesting character to pair with a vampire wife. Their natural enmity in most lore could create a lot of tension and drama in the story. But also, they could find common ground and fall in love, defying the odds.
Jacob could also make a great pairing. He has his own relationship with Bella, and his werewolf nature could create a lot of drama when interacting with the vampire sister. They might start off as enemies but gradually find common ground, like their shared love for Bella in a way, and then develop a deeper relationship.
Link from The Legend of Zelda series could be a great partner for Ryu Hayabusa. Link has his trusty sword and shield, and his ability to solve puzzles and traverse different terrains. Ryu Hayabusa's ninja skills would blend well with Link's adventuring spirit. They could be on a quest to rescue Zelda, who has been kidnapped by some dark force that also threatens Ryu Hayabusa's homeland. Their combined skills would make for an exciting story as they face various enemies and challenges along the way.
If it was a crossover with the Lord of the Rings, Aragorn could be paired with Darth Vader. Aragorn is a noble and skilled warrior, and his leadership skills would contrast with Vader's tyrannical rule. They could start as enemies, but as they learn more about each other's worlds and the threats they face, they might form an uneasy alliance to defeat a greater evil.
Sakura could be a great choice. She has strong medical ninjutsu skills and a no - nonsense attitude. She could help the six - tails jinchuriki when they get injured during battles against the power of the six - tails or external enemies. Also, her growth as a character could be further explored as she tries to understand and support the jinchuriki.
A character like Hook could be an interesting choice. He has his own complex past and a bit of a rogue nature. Pairing him with Drizella could lead to some interesting power plays and character development. They could either become allies in some devious scheme or Hook could end up being the one to make Drizella see the error of her ways.
Another interesting pairing could be Jeremy and Caroline. Caroline is already a vampire, so she could mentor Jeremy in a way. They could have a fun, flirty relationship where they go on adventures together and learn more about the vampire world as a team. It would be interesting to see how their personalities clash and mesh at the same time.
Neliel could be a great choice. She has a more gentle and kind nature compared to many other Arrancars. Her unique appearance and backstory would make for an interesting dynamic with Uryu. She could potentially teach Uryu about the different aspects of Arrancar existence that he may not be aware of.
Kakashi could also work well. His laid - back yet highly skilled personality would be a contrast to the more mysterious and often dark nature of a vampire. As a vampire servant, he could use his vast knowledge of ninja techniques in combination with his new vampiric powers. For example, he could use his vampire - enhanced speed to perform his Raikiri even faster and more powerfully, while also having to deal with the thirst for blood and how it affects his relationships with his comrades.
Bonnie would be an interesting match. Bonnie is a powerful witch, and as Silas' daughter would likely have some sort of magical abilities too. They could team up to fight against common enemies or to solve some of the magical conundrums in Mystic Falls. Their relationship could be a bit rocky at first, as Bonnie might be cautious about getting involved with Silas' family, but over time they could develop a deep bond based on respect for each other's powers.
Bakugo could be an interesting vampire. His hot - tempered nature combined with vampiric powers would make him extremely formidable. He might struggle with the bloodlust, which could add a new layer to his character development.