Convincing parents to let you date?

This is different first off all, im using my friends e-mail. Anyways, im 13 and parents think im just heir "little girl" im the only girl, the middle child of 3 siblings. My older brother is 17 and has only had 2 girlfriends, his first one was this year. I think my parents want me to wait until im 17, but i just cant, im not going to follow in his footsteps. Ive already had a boyfriend, i just haven't told them. I want to be able to go out on actual dates with my boyfriend and not have to hide it from my parents. I am responsible enough not to do anything stupid. I think they should let me date, can someone help me find ways of convincing my parents. Also, i don't want to have to sneak around. Thank you :)