I know you are still a teen. Even though I feel it isn't quite fair for you to be put in a position to give parental discipline to your own brother. Parental logic, and principles, can be used as to make him respect you, and your wishes.
Dr Kevin Leman has a book called " Have A New Kid By Friday". It basically teaches children that "B" isn't going to happen until"A" happens first.
The next time that he wants to do something fun, tell him "no, we aren't going to do that because you haven't been obeying my wishes." He can't have it HIS way all the time.
He should respect you if you are his caregiver. He should also be doing chores, and take responsibility for his actions, good and bad.
Your parents should be on board with you, and they should stop making excuses for his bad behavior.
If this book, and it's practices are something that you would be interested in, then let me know and I'll post some of it's helpful tips.
Here is the author's site:
DrLeman.com - Official site of Dr. Kevin Leman
All of this that you are going through right now is going to make you an even better person and parent.
You impress me with your maturity and insight. My wish for you is for you to be a happy, healthy, teenager.
God bless you.