If the younger brother joined then the older brother will stop sleeping with the husband, that's why the younger pretends to don't know what's happening because the younger brother is a jerk
Also the husband. If the older found out that the younger brother knows then the older will stop and the "thrill feeling" would stop and the younger brother and husband doesn't want that.
Just blindfold the older twin
Why do they look like Ivan and Till??? Anyway, this is so fucked up like wtf is wrong with Do-eon? Poor uke :<
Ivan Till this, Ivan Till that PLEASE STHU SON