What should I do about this summer?

My two younger brother is coming to stay with us for the summer ( I guess) and one of them is bring a best friend so that a total of three peoples. The problem is they probably have to sleep in my room my mom said she would get different beds for everyone but still I won’t have my private space. But there is a chance that two of them will be sleeping in the basement. This not the only problem. I barly know these kids (seriously we met last year and spent 1 day together) and I know my mom happy that she get to see her kids again ( she havn’t been able to see them almost all there life) so I want to try to be nice. But that is almost impossible for the whole summer ( I barly made it 1 day without snapping at them). The youngest one not much trouble but the 14 year old (nick) is. Alway talking like he so big and tough saying stuff like “oh ill knock you out ( I take threat from strangers seriously). and other stuff he think he can just push peoples around. Then he always want to talk about the way I speak (I got a speech impediment). I got a quick temper when it come to that I wanted to break his arm last year when he said that but I didn’t want to mess up my mom moments. I need some tips on how to deal with this? ( mostly the problems is with nick only)