![](https://pic1.mangapicgallery.com/r/avatar/90/u751733_50x50.jpg?2)
I have few reasons imma short list here
1. Brother beat up the guys in the academy who shit talked mc about her engagement
2. He blushed a LOT, like all she did was talk with him and that bro kept having cheeks as red as his hair.
3. In the manhwa verse it happens very often for the male step sibling to fall in love with his sisters. There's many disgusting manhwas out there in which the mc ends up with her step BROTHER like that manhwa where the mc has green hair and the ml was gay in the og novel bfr meeting her (brotha ew)
Or like Penelope and Derrick, Ruby and Caesar. Korean authors often make the step brother in love with the mc to spice things up.
After a while you will expect it when you see it
Please dont tell me the brother has a crush on her