We train people to treat us the way that they do. Up until now, your methods have produced this result. Your brother thinks you are his servant, and treats you like one. In fact, treating a servant this badly would be rude.
So you need to start re-training him. If he wants pancakes, he can have them. But he cannot tell you to make them. He can make them for himself, or he can ask you with the word "please" in the sentence, and you can decide whether making pancakes for him is an enjoyable use of your time. If you make them, and he doesn't say thank you, you can tell him that you are finished doing anything for him, until he starts treating you politely, and like a member of his family. Then stick to that. If he gets all aggressive and emotional, leave the room. Or, if necessary, the house. And if that's necessary, tell your parents that he needs help.
It's really pretty simple.