People use 'brother' to refer to men close to them a lot in many asian cultures/languages
For example:
Korean 형 - hyung - older brother - refers to a male friend or a male sibling who's older than you
Chinese 哥哥 - gege - older brother - term of endearment for someone you like or have a close relationship with; respectful way to address someone older or someone you admire etc
If you're familiar with Tian Guan Ci Fu/ Heaven Official's Blessing then Hua Cheng calls his lover Xie Lian Gege
It might be a bit awkward with directly translating it to English, since it's not often used in that way, but yeah
If you read it as hyung and it sits sooo much better
I know. That’s why I said mistranslation or they should have just stick with hyung
Ima pretend that the “brother” comment was just a mistranslation cause I realize even if it’s official, they still makes mistake