In many fanfics, Fleur is often depicted as strong - willed. She's a Veela, so she has that alluring quality, but she's also smart and not just a pretty face. For example, in some fanfics she uses her Veela charm in a strategic way to get what she wants or to protect others.
Often, Luna Lovegood can be found in such fanfictions. Her unique and dreamy nature could bring a different dynamic to the harem. Neville Longbottom might also be involved in some way, perhaps as a friend who supports the harem and helps them out in times of need. There could also be some foreign exchange students or magical creatures in human form that end up in the harem for various reasons.
Often, Harry's sense of responsibility grows. He starts to see the marriage contract as not just a burden but also an opportunity to create a new life for himself and Fleur. Fleur's personality may develop in a way that she becomes more protective of Harry. For example, when they face opposition from the wizarding community about their contract, she stands up for them. She also might help Harry to overcome his insecurities about being in a relationship with someone as glamorous as her.
At first, they might be at odds with each other. Fleur could think Harry is too impulsive, while Harry might find Fleur a bit too haughty. But then, when they are forced to work together on a mission, they see the good in each other. Fleur realizes Harry's selfless nature, and Harry sees Fleur's intelligence and determination. This new - found respect leads to a romantic relationship and ultimately marriage.
One possible reason could be that Fleur sees Harry as a powerful and important figure. In the wizarding world, Harry is the famous Boy Who Lived. Fleur might be possessive because she wants to be associated with his fame and power. Also, his bravery and skills could be attractive to her, making her want to have him all to herself in the fanfiction world.
They would probably have a close relationship. As siblings, they'd likely look out for each other. Fleur might be protective of Harry, and Harry would respect and admire his sister. Since Fleur is older and more experienced in the wizarding world in some ways, she could be like a mentor to Harry at times.
Bill Weasley is often included. Since Fleur was originally engaged to Bill, his presence can add some drama or interesting interactions. He might be a bit conflicted at first but eventually come to terms with Fleur's new relationship with Harry. Another character could be Ginny. As Harry's ex - girlfriend, she could have some complex feelings and interactions in the story, perhaps initially being a bit jealous but later becoming a friend to them both.
Fleur and Tonks might start off a bit wary of each other. Fleur, with her proud and somewhat haughty nature, could see Tonks as a bit too brash. But as they both love Harry, they would have to find common ground. They could start sharing stories about Harry's heroic deeds from their different perspectives. Eventually, they would become friends and support each other in the relationship with Harry.