A half-brother who is also your cousin. The male offspring resulting when your sperm donor also impregnated your mom's sister. The male version of a couster.
I used to get along really well with my cousin Jake, until I found out we had the same dad. Now he's my brosin, and it's kinda awkward.
A cousin who has the characteristics of a "bro"
My mother's nephew is such a brosin
Shopping/browsing with your bros but no homo.
Scott: Dude thats a sick sweatshirt. Is that new?
Taylor: Yeah, I got it this weekend when me and Luke were brosin' at the mall.
A friend or family member who maintains the highest standards by hooking up and having children with two members of the same family.
Jane Doe hooked up with John Doe, had a son..then hooked up with John Doe's brother
and had another son..therefore the kids are not only brothers they are also cousins
Brothers+Cousins = Brosins
Brosins - pronounced Brah-sins