I feel the same way even. The sister part but my sister is in high school and I am twelve I feel like if I tell my mom she will just say oh your fine that's normal and my sister she is so mean people think she is joking but it hurts also I had a friend who when she was being a little rude. And I wanted to leave I would go to get my stuff she would pin me down and then shei moved after we Were not friends anymore we were friends since second grade . Also I feel like I. Deserve it but I barely stop myself sometimes.
Ok, it is not normal for your age to want to kill yourself. It is not normal for anyone, so you need to seek help immediately. Therapists are very helpful. You say you are lonely, I think talking to a therapist who will listen to your every word and dedicate time for you would be very good. They can also get to the root of why you feel this way, and then help build you back up to be a stronger and happier person.
Have you tried telling your family that they go to far with you? Tell them it hurts you when they tease you and you feel lonely. If you dont say anything at all, you wont accomplish anything and will end up feeling this way for a long time.
Also, do not cut yourself. Really. It is such a temporary fix that doesnt actually do anything. Years down the line when you remember this time in your life, you will want to think of how strong you were to overcome it, you wont want to have those scars to think about how it controlled you. I have cut myself before and trust me, its not worth it.
I think this is a very emotional time in your life. Hormones are changing and of course your going to be more sensitive. Seek out the help you need, and do it for you. THis is your life, and you are too young to let it get to you!
I have already commented here but that's not the whole story would. You mind reading what I posted it is called (am I depressed and is my life normal)
You only get one life. Please don't go too far. I don't know you, true, but I'll be here for you if you need someone to talk to. I know what it's like to want to commit suicide. And I know what it's like to have a friend commit suicide. It is something that still gives me nightmares. Please, PLEASE don't go too far. No one should feel like no one cares. It's not fun at all. It's painful. But If you don't go through with cutting or the suicide, life is totally worth it. You've got a purpose here on earth unique. You're not going to ever find out what it is if you end your life.