It's hard to say for certain. The Harry Potter fanfiction community is vast and diverse. Some writers like to create alternative universes where characters have completely different relationships. But given the nature of Harry and Lucius in the original series - one being the hero and the other a Death Eater - making them brothers would require a great deal of imagination and explanation. The writer would need to explore how this new relationship would affect the plot, the other characters, and the overall themes of the story. It might also change the way we view the magical world's social and political structures as they are presented in the books.
A practical answer is Chapter 231, because it turns the idea into a concrete scene. The chapter opens with Huo Xuan felt a burst of secret delight in her heart., adds pressure through My apologies, my apologies." "Does the bigwig want his fortune told too?"..., and ends on A cool sports car was.
Chapter 251 is the strongest chapter-level answer because it starts from If Du Qinglian was somewhat angry just a moment ago, now she was simply at... and follows through on The moment the connection was successful, before even appearing on camera,....
A practical answer is Chapter 250, because it turns the idea into a concrete scene. The chapter opens with The knowledge that several guests were soon returning had fans arriving at..., adds pressure through Not seeing me for so many days and not even asking how I am, you think—"..., and ends on.
Chapter 237 is the strongest chapter-level answer because it starts from It seemed as if, believing the spilled water couldn't be recollected, Ah... and follows through on The netizens responded in chorus, and no one insisted on forcing Jiang Li....
A practical answer is Chapter 206, because it turns the idea into a concrete scene. The chapter opens with Five minutes later, Xingxing led Ah Fu out of the room by the hand., adds pressure through Miss Su, you're even better than us parents!, and ends on He was the oldest of several siblings and.
Chapter 256 is the strongest chapter-level answer because it starts from Turning around, Jiang Yan and Zhao Lang found their heads had been... and follows through on I was dazzled seeing Jiang Li trending today." Next door, Su Yinwan let....
Chapter 251 is the strongest chapter-level answer because it starts from If Du Qinglian was somewhat angry just a moment ago, now she was simply at... and follows through on The moment the connection was successful, before even appearing on camera,....
A practical answer is Chapter 212, because it turns the idea into a concrete scene. The chapter opens with Although she appeared outwardly flattered, in fact, her heart was already..., adds pressure through Could it be that the sister's anti-fan who cursed her on Weibo was Jiang..., and ends on.
The best chapter pointer here is Chapter 267, "Betting Agreement". It opens with Jiang Li had just turned around when she was suddenly embraced by a... and closes on —However, he was indeed about to experience some misfortune..