I can relate. =]
My sister is around..maybe 4 years older than me, and over the years, I had frequently felt like she had got more attention and more things from my parents.
As we both got a bit older, I realized that my parents didn't really love her more, she just excelled in certain things and my talents were kind of overlooked.

I agree with what the others said, Draw because YOU like it, and keep working at it until you are able to blow your parents away with your talent. You already have talent, and with a bit of practice, you could become an excellent artist. Maybe enroll in some art classes at school? Or even look up some drawing tutorials on the internet to help out with some details.

Maybe to help yourself feel more appreciated, once you feel like you've done a really great peice of art, frame it yourself! Find a place in the house and display it. When I thought I did a nice job on drawing something, I'd always find a nice frame and set it all up on my parents' dresser so they'd find it.

And never forget, your parents always love and care about you. =]