My Dad majorly favors my younger brother?

I try so hard in school to make my dad proud and my brother gets average grades, he doesn't play any sports, throws temper tantrums constantly and hes 10 years old! i'm almost 14 and i feel like i can't live up to what my dad expects of me. he always chooses my brother over me and i really can't take it. yesterday we were gonna go fishing and hes like well if the nanny doesn't show up then sam's just gonna have to stay home and watch the baby, and its ridiculous cause i would have to do that because the boys wanted to go fishing so i wouldn't get to? luckily my step mom always tells my dad that's wrong, but her and my dad are in the process of a divorce so shes not around as much but still pretty often. my dad is a little ist because he thinks boys are better a sports and he almost didn't let me go fishing yesterday because i was a girl. my step mom told him to treat all the kids equally and always lets him know that my brother is misbehaving and he still throws temper tantrums. i am really girly but i play soccer and tennis and my brother plays no sports so who is my dad to say that girls can't play sports? how can i tell my dad to stop the favoritism. what is so good about my brother? my dad has 4 biological kids and 2 step kids; out of the 6 my brother is the 5th and hes my dads only biological son and my dad also has a stepson.