I just think that "bro" is in most titles because of the uploader's screen name. I don't feel it's anything more than just an identifying tag or theme. As Wichser69 observes, "nerd" is internet porn code for guy in glasses, just as "chub" is a dude without washboard abs.
Can't answer the Bro bit, but it appears that anyone who wears glasses on GBT is classified as a nerd and has a big dick. Btw, I wear glasses. I won't go on.
why is he nerdy? Because of using glasses. Is that it?
why are u, uploader, stupid?