Why do abusive people that cross boundaries think they are normal?

I mean are they sociopaths? If someone molests you, or a family member makes suggestive comments and innuendos, or ogles you or puts you down but otherwise they are very friendly and social when they need to be to the right people what can you do about that? My family members are like this. I am the only one that knows who they are really are at their core and I have been victimised as the youngest in the family and have no support. My other siblings, and parents are part of this dysfunctional system and day after day I am more and more depressed and thoughts of suicide are more and more prevalent because it is like they will violate me in some fashion with a smile n their face, have lively discussions, quite social, and then act like I have the problem. That I am the weird one in the family, I am the failure?? It just isn't fair really.