Responses
Hi, it seems the plot of Reunion even though they didn't meet as kids but in their 20s. https://www.mangago.me/read-manga/reunion/
Even if it's not the BL you're searching for I recommend you read it, it's amazing imo!

There’s a Korean BL I remember being popular on here about a guy who had to crossdress as a kid while pretending to be an old man’s relative(?? Not sure about that part) and while he was there there was also another boy there with him(the ML). These two later grow up with the MC trying to move on from his past while the other is still desperately looking for him, and they come across each other while the MC is working at a bar and the ML mentions that he looks like the girl he has been looking for the whole time. I’ve been trying to find it for a bit, and I just can’t seem to remember the name of the BL. Would any of you happen to know the BL I’m talking about?