Why are my half sisters treated better is it cause there mixed and im black?? is it bad that i hate them?

ok im 16 and when i was like 3 my father passed away and when i was about 5/6ish my mom got remarried to a white man. and ive never liked him and he's the nicest guy either. and when i was 7 they gave birth to the twins (parker and maliyah 9yrs old). my life got even worse from then.my step dad treats like were two worlds apart. every summer he sends them across the country, world , wherever for family reunions, beach whatever. while i stay home and they all have the time of there lives. my sisters go to rich private schools while im stuck going to public. my step dad always buys them the expensive toys, clothing. and when we argue he'll jump in and yell at me to the point im in tears and tell me to go to my room..and my moms doesnt do anything to defend me. he even hit me once for slapping maliyah in the face for breaking my stuff. even on christmas they get more stuff then me this christmas i had 4 presents in total (that my mom bought) while the twins had 10 each!! and the twins are bratz and are mean like there father, to be honest when nobodys home i beat them up bad! and its like everyone likes the twins and pays more attention to them is it cause there mixed? i mean im pretty lightskinned i just dont have there good hair. how do i deal with this situation? is it bad that i hate my sisters? how do i deal with my step dad? is it bad that i hit them when nododys home? cause they put me through HELL!