Whats wrong with my wi-fi?

I love video games and I live with a big family, like huge, but there's only one wi-fi network. I absolutely hate my uncle, he always steals my stuff now I don't know what he did but he stole my connection to the household wi-fi. I enjoy playing Overwatch and wow with my boyfriend and we haven't had any problems until my uncles girlfriend came to visit for the month from Dubai and now we constantly lag. It is super irritating. I needed a way to turn down their connection cause all she does is suck up the connection making international calls and what not on her computer, phone and I-pad not to mention my uncle also plays PC games and at least 20 other devices are connected to this network and it has become impossible to play video games with my boyfriend.... I looked it up, I couldn't figure out what our password was for the IP or any of that so I just downloaded this app called NETCUT which was working wonders. I totally limited my uncle and his girlfriend and had the best FPS and MS I have had for the past month(only lasted one night). All last night he was so frustrated he and his girlfriend could only get 3 bars of connection instead of 4 (how nice of me to not limit them to 1 or 2 right?) anyway, he called our internet service provider and reset the IP password and all that stuff so he actually has full control now and I don't know what he did but every time I log into Overwatch it takes like 20 minutes to load if it does, and as soon as my boyfriend logs in, I lose connection to the game server or if he logs in first then me, he immediately loses connection. What exactly did my uncle do? What did he limit so we cant both play at the same time? I really am sick of this guy thinking he can take whatever he wants from me and the only thing I had left was playing video games with my boyfriend on this wifi. How can I reverse this? He is affecting the rest of the household. I have a feeling he gave himself the entire broadband connection and limited everyone else. PLEASE SOMEONE HELP ME.