I just need to know did they find out that they were brothers?

I think so, because at the ending, they called each other by their original names when they were doing their farewells. Namsoo even called him hyung.

That is true ... but God it's hard remembering they name and what they could each other (￣∇￣")

Namsoon found out his real name and from which orphanage he was adopted by the paper..

Didn't y'all read the part where he took the paper from his adopted father's hand after the adopted father rot to dead? That's where Namsoon found out that his name was Lee So- (whatever) U guys Ned to pay attention! (Jk.. I'm just scolding y'all coz it's fun)

Btw I also think that Hyunheo(whatever the name was..) knew that he was adopted. It's easy to understand from here, once people finds out their adopted wouldn't they want to know their biological father, mother and if they had siblings?

True... But it would be better if they just showed us ┑(￣Д ￣)┍ that way we wouldn't have to make up some sensible end but all good they know who they are to each other so All cool (=・ω・=)