Am I a good babysitter????

I have to watch my sister and brother when my rents and older sis are out. I can handle my sister(she's 2) but my brother is eight and out of control.he puts ice down me and the lil sis' shirts, pees in cups( for fun),lets my dog loose outside(we have a gator infested bayou across the street), uses my hair dye to dye our rabbit pink and blond and blue.And I am not allowed to or put him in timeout.But when my parents get home and i tell my mom she says that he doesnt know right from wrong yet and he is in gifted at school.And that i am older so i should be more responsible. And my dad says that it is just a stage he's going through because he is the only boy in a family of 4 kids.M older sister just says that i am a bad babysitter.What am I doing wrong? Am i a good or bad babysitter.