A spin-off on the word HoYay. It means the same thing, but is more specifically describing scenes between brothers. Commonly seen in the Supernatural (Dean/Sam) and Heroes (Peter/Nathan) fandoms. A more specific genre of BroYay is: Twincest. Most commonly twin brothers like in the Harry Potter (George/Fred) & Boondock Saints (Connor/Murphy) fandoms.
The broyay exploded in radioactive delight. Yay for homoerotic brotherly love!