I can sort of relate in some parts of what you said. My sister tends to invite my cousin over about every other weekend, and I'm stuck with her because no one else will do anything. Don't get me wrong, I love her, but she can get REALLY annoying and doesn't know how to be her own person. I also had to move into a house with my mom, sister, and mom's boyfriend, which was already filled with my grandmother and two uncles. It was SO cramped, Then when we moved out, the grandmother and one uncle moved into our house, and the toehr uncle and his gf are over almost everynight nad never leave. Try asking your sister, in a nice sisterly way, if she can quiet it down a bit at night. She should be able to understand...try talking to your mom too...I wish I could help more...
I also had to move into a house with my mom, sister, and mom's boyfriend, which was already filled with my grandmother and two uncles. It was SO cramped, Then when we moved out, the grandmother and one uncle moved into our house, and the toehr uncle and his gf are over almost everynight nad never leave.
Try asking your sister, in a nice sisterly way, if she can quiet it down a bit at night. She should be able to understand...try talking to your mom too...I wish I could help more...