Why do my friends and sister always insult me?

alright i chill with my friends and they always put me at a down point and also my sister joins them and tells me how idiotic i am and how that i dont have a life and i shouldn't even exist at all. Some of them told me to punch back and fight back when them punched my arm and i said no because im not the fighting type at all i know they joke around but i get the feeling they do it too much. I dont know if they are my friends and my sister we constantly argue with me and when she hits my breaking point i yell really loud and sometimes when she yells back i push her and tell her to shut up. I just got over my depression and i dont get them alot, i just wish i had a supportive sister and better friends i always wonder why does my life revolve with these immature people i know im the oldest in the group and they call me a chicken when i dont punch back. Sometimes i feel like they aren't my true friends and i always question when and how can i get true friends? i dont know what to do oh and my sister acts like i dont exist at all she completely ignores me like im not part of the family