Since houses play a major role in a student's identity at Hogwarts, for Harry, Draco and Blaise being triplets would mean redefining that identity. In Gryffindor, Harry has always been the hero figure, but with his Slytherin brothers, he might face some pushback from his housemates who are suspicious of the Slytherin connection. Draco in Slytherin would also have to deal with his own housemates' reactions. And Blaise, regardless of his house, would be in the middle of this complex situation. Their journey as triplets would be about finding a balance between their house identities and their family bond.
Perhaps they were separated at birth due to some dark wizard's plot. As they grow up, they start to notice strange similarities in their magical abilities and instincts. When they find out they are triplets, they join forces to uncover the mystery behind their separation. They might face many obstacles, like opposition from their respective families who have different beliefs and values. Harry's Gryffindor - like courage, Draco's Slytherin cunning, and Blaise's own unique traits would all play a part in this adventure.
In fanfiction, anything can be possible. Writers might rewrite the backstories of the characters. Maybe they could create a scenario where some powerful magic was involved at their birth that made them triplets despite their different families in the original story. For example, a dark wizard could have experimented with a spell that merged three different pregnancies into one, creating the situation where Hermione, Draco and Blaise are triplets.
The relationship between Harry and Draco would change drastically. Instead of being rivals, they would have to come to terms with being brothers. There would be a lot of initial tension as Draco's Slytherin upbringing clashes with Harry's Gryffindor values, but eventually they might learn from each other. Hermione, being part of the triplets, would act as a mediator between them.
A frequent plotline involves their family drama. With Hermione being a Muggle - born and Draco and Blaise from pure - blood families, there would be a lot of family issues to deal with. For example, how would the Malfoy family react to having a Muggle - born as part of their family? Also, they might be forced to work together to protect their family from threats. Maybe an old enemy of the Malfoy family targets them because of their new family situation. There could also be a plotline where they explore their magical abilities together and discover new and unique forms of magic due to their special connection as triplets.
If Harry were Draco's older brother in this fanfiction, their relationship at Hogwarts would be a total mess - up of the original dynamic. Harry would be constantly torn between the Gryffindor values he adheres to and his family bond with Draco. Draco might start to question his Slytherin - only ideology because of his connection to Harry. For example, they might find themselves in situations where they have to choose between their house loyalties and their new - found brotherly bond, like during the Quidditch matches or the Triwizard Tournament.
One common theme is friendship. Many fanfictions explore how these three characters, who start off with a lot of animosity, especially Harry and Draco, can form a friendship. Another theme is rivalry turned into cooperation.
I think 'StarlightAuthor' is really good. They write stories that are very detailed, especially when it comes to the interactions between Harry, Blaise, and Draco. 'SunriseWriter' is another one. Their fanfics are known for their creativity, like creating new magical elements that are intertwined with the relationships of these three characters. And 'MidnightScribe' is an author who does an excellent job of bringing out the different personalities of Harry, Blaise, and Draco in their stories.
Well, in this kind of fanfiction, Draco and Blaise saving Harry and leading to a romance could be quite a wild ride. It might involve some magical adventure where they team up against a dark force. The change in their relationship with Harry could be gradual. At first, they might be reluctant allies, but as they face danger together, they start to understand each other on a deeper level. The romance could be a result of shared traumas and the realization that they have more in common than they thought, and it's a fresh take on the relationships within the Harry Potter universe.
One common theme is redemption. Often, Draco is shown on a path of redeeming himself and his relationship with Harry and Blaise plays a part in that journey. Another theme is friendship. They start from being enemies or at least indifferent to each other and develop a deep friendship over time.
One great fanfiction is 'The Unlikely Bond'. It beautifully explores the complex relationships between Harry, Draco, and Blaise. It shows how they overcome their initial differences and form an unexpected friendship. The character development in this fic is really well - done.