Okay, so. The Janitor in the ark is the MC's biological older brother, and in the original timelime, the MC took his name in hopes that his brother would notice and eventually track him down but he never did. As a kid, the MC probably held out hope that his brother would find him eventually but as time passed and he got older, he probably just couldn't be bothered to change back his name out of either inconvience or longing.
The reason why the MC never mentioned having a brother is fairly simple—this entire manhwa is about unpacking his past. His brother just wasnt relevant in the beginning of the story and was thus not mentioned. An in story explanation is that he could be resentful towards his brother for never coming back for him, and thus supressed his memory of him. His brothers exists in both timelines, and in both he never returned.
There is no butterfly effect. My theory is that his brother died, or thought that the MC would be safer without him.
I finally get it, thanks for the explanation
Nah no problem, its one of those revelations that you get really confused about if you don't read it all in one go, or have good memory. (づ￣ ³￣)づ
wait I'm so confused so he took the identity of the janitor in the ark? but then where is the janitor hajae and why doesn't he appear in the previous timeline or is this a butterfly effect? but ilrok (mini-hajae) remembers having an older brother but MC didn't mention having any..? what is goin on