Should i ever talk to my family again?

ok here is my story. my mother is an alcoholic but wont admit it and has been for as long as i can remember, she always put grog and men before her children. my younger sister and i were taken off her and placed into foster care when i was 9. things didn't work out for us so my little sister went to live with my older sister and i went to live with my aunt and cousin in the same town. while living there my 23 yr old male cousin did some pretty bad things to me without my consent, i was 12 at the time. i confided in the school councilor and of course it all came out in the open. my aunt and her daughter (male cousins sister) didn't believe me and i was sent off to foster care in a different town. years went by and when i was 16 i went to live with my mother and sister again but in another town away from all the drama. we became a family again apart from my mum still drinking. i me this wonderful guy and we moved state when i was 19. since than my mum and younger sister moved back to the same town where all the drama started. they both started acting weird and not really wanting to talk to me over the phone. they didn't even say happy birthday to me or anything. i was talking to my sister a couple of weeks ago and asked if she had seen my cousins or my aunt and she said no she would never talk to them again and how much she hated them but the other day she posted a picture on facebook off them all out at the pub and saying how much of a good night she was having. iam really hurt and feel betrayed by the people i thought i could trust and im really getting sick of making the effort to contact them when they never seem to care. i guess my question is should i forgive them or just get them out of my life for good?