My parents, whom I'm around pretty much all the time, are very odd, negative, rude, and it' rubbing off on me?

Hey look at the bright side...at least you've realized it. They likely never will see how negative they are or enjoy it and will be that way for the rest of their lives. You are young and you have your whole life ahead of you. Make the effort to become more positive. Try to stay away from your parents and their toxic vibes as much as you can. You can do it. :)