what could be using up my internet?

[Antonio]

Porn, youtube, and especially MegaShare or any other types of file sharing software takes up a lot of data. Megashare can take up a whole lot of data if he's downloading music constantly or movies (take up a LOT of space). I'd have to say that you're brother is eating up all the internet.
I'm guessing Megashare is like Uttorent, where you can illegally download music, movies, programs, ect. If you don't delete your torrents, then they will "seed" meaning that you're system is always trafficking data constantly. When you seed, people can download parts of whatever you downloaded from your machine.
Your bro is causing all the problems. Lol good luck

EDIT: My bad, I confused megashare with a file sharing application. But still, megashare eats up a whole ton of data.