People use 'brother' to refer to men close to them a lot in many especially 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
"brother"!?!?!!!?? BRO WTF?? IS THIS OFFICIAL HAHAHAHA I'M DYING IMAGINE FINGERING YOUR BROTHER'S BUTT