A Brotaku is a person who is too cool for school yet at the same time is too nerdy to be a geek. Brotaku's have a great deal of status and are able to have a pokemon collection and still pull it off with extra swagger.
the word is basically a marriage between Bro and Otaku Where a Bro is your average cool guy in any "group of friends" or cliques and is a very popular person as well as a nerd in any category , gaming , anime , manga , or any of the subtypes that is defined as "Otaku" by Japanese terms.
you know that kid chris?
"yeah thats the kid with all the tatoos and like works out all day and gets every freaking girl."
did you know he loves anime ?
yeah that kid is a brotaku.