My younger brother and i have a strained relationship?

our relationship these few weeks have been so strained. i criticize too much and he's quite pive aggressive which makes me appear crazy and a bully in front of our mother. i think this strain is due to my mother's blatant favoritism for my brother. i'd love some advice on how to repair my relationship with my brother, as i do believe family is important, and now at 17 would like to try to make my family what we've always wanted to be: a tightknit, close and loving family which at the present moment we aren't. my brother and mother now are, i'm not included.