Lucius has a sense of entitlement that comes from his pure - blood upbringing and family wealth. Hermione, being a Muggle - born (in the original story), has had to fight for her place in the wizarding world. So in fanfiction as siblings, Lucius might initially look down on Hermione's more inclusive views, while Hermione would be appalled by Lucius's prejudice. However, as the story progresses, they could learn from each other. Lucius could become more open - minded and Hermione could understand the pressures of a pure - blood family.
One interesting plot could be them discovering their relation later in life. For example, Hermione might be adopted without knowing her true family ties. Then, through some magical mystery, she finds out she's related to Lucius. It could lead to a lot of inner turmoil for both of them as they come from very different worlds within the wizarding community.
For Lucius, his development could be a slow process. At first, he resents being around Hermione, but as he witnesses her magic and her kind heart, he starts to question his own values. He may begin to see the error of his ways regarding blood purity. Hermione might develop more patience. Dealing with Lucius, who has such different views, makes her learn to tolerate and try to change someone rather than just oppose them.
One interesting plotline could be the clash of their different ideologies. Hermione, with her strong beliefs in equality and justice, and Lucius, from a traditional pure - blood family with elitist views. Their marriage, forced by the law, might lead to a power struggle within the Malfoy household as Hermione tries to assert her values.
Hermione could also use her magic skills to her advantage. She is a powerful witch, and in the Malfoy household, she may use her magic to create a space for herself where she can be true to herself. She might also use magic to subtly influence Lucius and make him more accepting of her and her beliefs.
Well, perhaps he uses his influence in the wizarding world. Maybe he has some connections or knowledge that allows him to intervene and get Hermione out of the abusive situation. For example, he could use his status among the pure - blood families to put pressure on the abusers.
At first, Lucius might be shocked by Hermione's flirting. He's used to a certain type of pure - blooded behavior, and Hermione, as a Muggle - born, is completely different. But as she continues to flirt, he could become intrigued. He might start to see her in a new light, not just as a Mudblood but as an intelligent and alluring witch.
Yes, there are some fanfictions with this concept. Some writers like to explore unique pairings in the Harry Potter universe, and this is one of them. However, such pairings often deviate from the original storyline and character relationships in the books.
Snape, Hermione and Lucius interact in really interesting ways in fanfiction. Snape might initially be distrustful of Hermione due to her friendship with Harry, but then come to respect her intelligence. Lucius, being a Death Eater, could see Hermione as a target or a means to an end. In some fanfictions, Snape has to protect Hermione from Lucius' schemes. It's all about how the author wants to twist the relationships between these very different characters.
In fanfiction, the relationship between Hermione and Lucius can be quite complex. Some fanfictions might explore a scenario where they are enemies forced to work together due to certain circumstances in the wizarding world. For example, they could be paired in a mission to save Hogwarts from a new dark threat. Their different backgrounds, Hermione being a Muggle - born Gryffindor and Lucius a pure - blood Slytherin, would create a lot of tension and interesting character dynamics.
Another idea is that Hermione is there by accident. She could have been exploring the Malfoy Manor (where Lucius's office is located) out of curiosity or in search of something related to Harry Potter's past. Once in the office, she discovers a hidden secret about the Malfoy family that could change the course of the wizarding war.