@Chrana That's possible, but isn't the timeline where he's friends with Lamia one where she becomes a duchess? That would seem to imply the brother became a knight (since Lamia is only trying to become a knight to force him into the duke position) and never had his hand injured.
Plus, I doubt Lamia would become friends with someone who did this to her brother. Heck, we literally have proof of this considering how she acts around him right now despite the "uwu sad boi" persona and helping her father. He's trying to approach her because he wants to save or help her here, but it doesn't explain why he wrecked the brother's hand in this timeline versus the other timeline where he first got acquainted with Lamia.