How do I tell my Dad that my brother is downloading.

My dad has a strict no downloading policy. Because of where we live our internet connection is weak and downloading slows it down to a snails pace. My dad works on the computer so if he notices it being slow he will disconnect all other computers. Trouble is that I'm home schooled online and it's very difficult to study when my internet is off most of the day. We already have 11am to midnight timers on our internet, so it's not like I can make up the studying I miss at night. I know it's my brother who is downloading. I noticed a month or so back that he had 'u torrents' installed on his phone. When I asked him about it, he said he needed to install updates on his phone. I have the same phone as him and i don't have to do anything like that.... He also manages to find a lot of movies to watch for someone who doesn't download. I tried asking him to stop but it's no use, I need to tell my dad, but he's very strict and I don't want my brother to be in trouble. Please help I have an essay I need to finish.