i was thinking maybe because ideum had to get a heart transplant, he missed a year or two of school and ended up in the same class as the ML? then the brother got brought up, and he also had some kind of illness and couldve also been held back, so im not sure anymore. authors choice in hiding the brothers face makes it more confusing
I agree that hiding his face is sus!! I'm not saying it's definitely not him, I just think that w the context we have it's unlikely. Also if ideum got held up, it would make him the older one, not the brother. But he seemed to be rly young when he had the surgery so I don't think he actually did.
So it's only possible if Jaeyi's brother got for some reason held up by 3 years,, iono
They do look pretty similar and if he was so sickly he had to take three years off, it would make sense.
But also I'm interested to see what the author would do with that fact. I mean Ideum himself said that it wasn't deep or anything, so it would have to do something with Jaeyi- He seems not to be super fond of his brother.

im not the only one thinking that the ml’s older brother is mc’s first love right? he gotta be at least relevant for him to get this much mention