Yes, your dad is your bro, but so is your mom, sister, ofc your actual bro. If you look in the mirror there's a bro staring back at you and if you go outside you wave to your bros next door before going to work.

Seriously though its some reflection of society, idk what kind, and makes me think of the Goodburger song but swap bro for dude. Anyway, brother is rare, I hear bro/bruh everywhere though.