I am a stay at home mom, my job is cooking, cleaning and caring for my children. I would not tolerate this behaviour from anyone in my household. The person doing the work has an expectation of cooperation from the rest of the people. In my home you put away your own clothes, you put your laundry in the hamper and you clean up your own messes. Your family's treatment of you beyond what anyone should be expected to do.
Your brother must be sixteen or seventeen, and has learned you are a maid and not to be respected. He is capable of doing his share.
If you feel like doing things to help them, go ahead; but draw a line. Don't clean up messes left on purpose. If your brother can't figure out where the trash can is, it is not your fault or responsiblity. If you clean his clothes, he can put them away. If not, don't bother to rewash. If he is too lazy to move clothes from the dryer to somewhere appropriate, don't rewash them.
Cleaning and helping may be a reasonable expectation for all of you. What is not reasonable is expecting you to tolerate and take care of chaos and disorder created by laziness and disrespect. Your brother is an ass, and you are allowing him to be. No more doing his homework, no more picking up his litter, no more cleaning clothes that he can't be bothered to put away. If someone smells a bad trash can, they can take it out. Why is it your fault?
Why is your brother allowed to treat you this way?
Why are you doing his school work? It is his only job, you are only making things worse by enabling his laziness.
Who does these jobs when you are not there?
Why do they think that making extra work is ok?
Why are you paying for gas in a car that your brother is using?