Do i have Middle Child Syndrome?

so i am a middle child of 3 sisters. the youngest is 5 im 13 and my older sister it almost 15. i get in troble for my little sisters actions. like in the car the seat belt got tight on me so i unbuckeled it and rebuckeled it. my little sister knowing my stepmom tells me that i should be a good role model for my lil sister unbuckeled hers. so my stepmom flipped on me!! and then my older sister is always busting my and my stepmom hears and dosent do anything. but then when i bust her back she snaps at me. and many other things. do i have MCS and how do i solve it?