Responses
I know it is based on Korea and I know they use Hyung both Hyung and Oppa translates to big brother. Oppa is commonly used by females to address elder males meanwhile Hyung is used by men for older men. Both these terms Nothing has to do with blood related siblings. One common factor all across Asia is that our language background is the same, that's why I explained the context
Ok As an Asian I will explain the context of "brother" here. I'm South Asian and all of us Asians including East Asia has our own word for "brother" however that word doesn't mean Blood siblings. Unless you call your own blood brother, as in the sibling who is born from the same womb. So if you adress some male who is older than you & is not your blood by "brother" It's completely fine because both the party & the society knows that they're not related to blood. Even wife's call their husband's "brother" in their respective Asian language if they're older. However I understand in the west the term brother is seen as different.