Feeling suicidal, cant take my family life anymore?

Im 18 and honestly, my family are different people. I'm a different person from my sister and she posseses characteristics i cant stand, and same with my parents, they dont understand thier kids, they just ume they know, but when we try to explain, they just say "oh im your mom, i know you best" but in reality, they really dont get it, they just ume... And with my sister, we always fight, i try not to, but honestly, every week one way or another, we fight and every couple months we fight abut things really deep about our family that the whole family yells and cries. And the thing is, i dont try to hurt any1, its just the fact that people do not chose thier family, only thier friends. So obviously, if you dont chose your family, you will have differences and fights. its just our fights are so dramatic and horrible. My mom thinks we're "bad kids" since we always fight, she doesnt realize we dont mean to, it just happens since were soo different. i cried so much today as wel as the rest of us and i cant take it anymore, ive gone through 18 years of this & am just so fed up especialy when my mom gets upset. I dont knnow, i just want to end it, have u ever had this kind of horrible family life?