I can't handle it anymore... I am dying

I am a boy 18 years old.I have a problem which you can think as weird. When I was 11 years old.I was very depressed.My parents were quarrelling everyday. One day,I asked my little brother(7 yrs) to show his private parts and we touched each other genitals.We also played doctor patient game. After 2 or 3 months,we were caught by our father.Since then we stopped doing this. But after that we were quarrelling with each other and do not accept each other. Now,after 8 years,we are still enemies.He doesn't want to talk to me and I also doesn't want. My mother is sometimes upset as I am doing the house work alone and he doesn't want to work with me. I was once a bright student but it has affected me very badly.My health is also down. Also,me and my sister have done the same thing but we don't act like this way. I am very depressed because of it. What should I do? My parents are still fighting every month.