Due to our current economic climate, Monster Energy Drink sales have dropped over a jillion percent, which means that many bros are out of sponsorship money. Unable to perform extreme sports, many bros are opting to lie low in college until it's safe to come out again. Your dorm...yes yours...may soon become infested with bros by the hundreds...
Here we have a solitary bro, flexing to attract a mate. He wears a ninja thing to draw attention away from his face and toward his body.
He is soon spotted by another bro. The second bro lifts his arm to release sexual pheromones. The smell of sweat and Axe body spray is almost overpowering.

Wasting no time, the bro seizes his chance and prepares for penetration.
But we forget that bros don't perform intercourse like normal humans. In an amazing show of acrobatic prowess, the bros position themselves for the transfer of genetic material through fellatio. Note that the bros are holding hands, a sign of extreme arousal.

One of the bros is now pregnant, though it is impossible to tell which. The couple now stomps the ground, testing for the softest spot on which to build a nest and lay eggs. In a few short weeks, a clutch of newborn bros will overrun the dorm.
If you see the beginnings of a bro infestation in your res hall, frighten them off by telling them that you will break their white framed sunglasses. If this fails, simply kill them with fire.