Why do parents have their favourites and why does my family not care?

My parents have never been supportive of me, from the age of 7 they used to beat me and verbally abuse me - I was a neglected child. 11 years younger than one of my siblings, I've always been told that I was an accident and that they never wanted me, it's obviously true. I've never had a normal relationship with my parents, I hardly speak to my dad and do not get on with him, he always puts me down and clearly favouritizes my sister, the second child. My mum favouritizes my older brother, the first child, and I've always been left in the shadows. I feel so ****, like I'm never good enough, I never used to get hugs and as a result I hate hugging people/getting close to them.

I've been through my fair share at high school in terms of school and an abusive relationship which they know nothing about. My siblings don't care, my brother is married now and has his own family and hardly texts/calls, he obviously doesn't care either. My sister now is so self absorbed, she's literally hurt my parents so much and was suicidal in recent weeks and self harmed and immediately told them - I used to self harm but I wasn't an attention seeker and never told anybody. I don't have any sympathy for her, I know it sounds messed up but I don't know if I'm a product of my life experiences which have led me to become so angry and uncaring or if it's something else. Despite the **** she's done and is about to do, they worship the ground she walks on.

My family is just so ****** up and is so seperated, my brother is on very bad terms with my parents and doesn't speak at all to my sister. I feel like I don't have anyone and just resent them all.