How can I get my sister to treat me as her equal?

Because I'm the youngest in my family, they treat me like a kid and it sucks! My parents think I can't handle a week alone so I have to live with my sister. My sister does not treat me the same way she treats our brother or our cousins, she treats me like I'm a kid. I'm 14, I'm super mature for my age but nobody lets me prove it.
How can I get my sister to treat me as her equal?
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