I'm a middle child too and I totally understand. I have one older brother and one younger brother but the younger one is a step. My older brother and I go back and forth from our parents houses and my little brother just stays at my dad's. Since my older brother is at my dad's house more, my dad seems to like him more. My little brother is of course loved most because of his younger self. My dad and I never talked until one night I was just done and I didn't talk. Just get their attention and they'll think something is wrong and talk to your parents about it. They'll change. My dad and I used to fight all the time, then we had a long talk about getting help and talking to each other and acting happy. Now I actually have a relationship with my dad and step mom. And trust me, just telling your parents about it will help.