Wdym?
Hahaha... it's heavily implied huh...i think we all get the real meaning of their relationship.
YOU ARE REPLYING TO THIS 5 YEARS KATER SO I DECIDED TO RE READ IT TO SEE IF I WAS JUST DUKB BACK THEN AND I AM STILL CONFUSED WHAT OP MEANT
I think it is implied that they are brothers since the Uke called the Seme "Nii-san" and in Japanese it means "older brother". So he called him "older brother" and got pissed when he called him that since they wanted to forget it.Wanting to forget tells us that it is something forbidden/shameful. They prefer to be "strangers" rather than facing their real relationship, hence why the Seme made the Uke roleplay everytime into someone different and the Uke is okay with it.
H U H. Man i was really reading some crazy shit back then
To the author: you really going to ignore it? "I'm your..."