It sounds like you're feeling frustrated with your current situation. It's definitely understandable to want to earn some money and gain experience from a Saturday job. Here are a few ideas that might help you address this situation:
Communicate with your parents: Have an open discussion with them about how you feel. Express your desire to have a job and the benefits you see in it, like gaining experience, learning responsibility, or earning money for something you'd like.
Compromise: Offer to take care of your brother and do your homework, but propose a limited amount of time during which you can also work. For example, you could suggest doing an hour or two of work after you've completed your responsibilities.
Explore options: Look for ways you could babysit or tutor younger kids in your neighborhood. This way, you can fulfill your role as an older sibling while also earning money.
Plan ahead: If you can complete your homework and help care for your brother in advance or at different times, show your parents you can manage your time effectively.
Consider other activities: If you can't get a job right now, think about other productive ways to spend your Saturdays. You could volunteer, join a club, or take up a new hobby that could also enhance your skills for future job opportunities.
Ultimately, having a calm conversation about your desires and your responsibilities can help you find a solution that works for everyone. Good luck!