Is it legal to film an inappropriate act in our house? Is the video enough to get them to court?

I'm 19 years old and I live with my family. My younger brother, 18 years old, and his girlfriend, whom says has a major in psychology, continues to have sexual interactions even in the living room. It's obviously inappropriate and I want to have her restrained from this apartment that I live in. She is very un-shameful. Is filming them in their act in the living room enough to get them in court? And most importantly, is it lawful to film them? All that I want is that she does not lay foot into this apartment again. My parents think that their behavior in the living is wrong as well, but they will let the wrong behavior happen in the living room.