A word of endearment for your brother- by blood relations or friendship.
Daniel(Eldest Brother) - "What's up broster! How was work?"
Michael(Youngest Brother) - "Yoooo, what's up broster!! Work was fun and easy today!"
(n.) Descriptive noun. Family role, sibling; term of endearment for a transgender sibling.
The term is interchangeable and can be applied to any person who identifies as transgender or non-binary. Modernly adopted from more common parlance to represent much needed terminology for the identity changes an individual may experience over the course of their life.
Ex: He is my biological sister, but he's always been my brother. He's my broster!