The moment when they first realize they are comfortable enough to cuddle. Maybe they are at a Hogwarts party, and the music is slow. Harry and Fleur find themselves alone in a corner. Fleur, with her Veela charm, gives Harry a soft look, and he shyly puts his arm around her. They fit together perfectly, and at that moment, they both feel a sense of peace and a new connection.
You can try looking on fanfiction websites like Archive of Our Own (AO3). There are often many tags related to Draco and Harry, and you can specifically search for fics that involve them cuddling. Just use the search bar and type in relevant keywords.
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.
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.
Maybe they are celebrating a victory, like the defeat of a dark wizard. They are so overjoyed that they hug and then it turns into a cuddle. This shows the closeness of their relationship and how they share their emotions, both good and bad. It also emphasizes their friendship and the trust they have in each other.
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.
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.