The expendable sister

I don't think I can take one more day living with my sister and her family. I'm tired of being treated like I'm the lowest of low. My husband is also tired of the BullS--t too. We have no where else to go except back to living in our small car. I'm almost at the point where I would rather go through the horrors of living in the car again. What gives certain people the belief that they are good, deserving, caring and kind when for the most part they are just the opposite? Can they not see how cruel they are?