My little brother

Some people say their siblings are problematic, well then you havent met my little brother. He is currently 8 (turning 9 this year) and has caused my mom, dad and I mental breakdowns. He is so selfish that he will bother and and continue to do so if asked to stop my dad when he is in pain (he refuses to go to the doctor but I dont think he is okay) because he doesn't wanna go to bed. Well then you say 'its just a tantrum' it is not just this. He will bother you and keep asking you even when you say he cannot. He steals your stuff just because he wants to use it and doesnt even ask. He comes in when you told him not to, doesnt do what he is told to do, and honestly he doesn't care as long as he gets what he want. It is tearing the family apart, he is breaking my parents marriage by only caring about himself and not thinking about what may be going on in someone else's world. Im tired