[IncubusGod]

You're quite a lot older than her, her parents naturally assume that such an older man would be one to look after her.
Clearly you are not fitting that brief. They obviously do not want a man 9 years older than her to be someone who considers her "a bit of fun".
So they are bugging you to be more involved in their family life. Clearly they are trying to ensure you're going to be around for quite a while longer, and evolve into a meaningful relationship.
That's what parents do.

So it's a case of this, either step up and work things out with your young girl, or call up some serious questions about where you are heading with such a girl.

Family is clearly a big part of her life, no matter what you think about them. You can't just dismiss them or their impact on your relationship. Stop complaining about what you percieve as interference and accept it as what it is, family looking after their own.
It's not going to change cause you don't like it, and if you make her choose them or you, I'm afraid it will never be you.

My advice is to look at what you want out of this. If you see a future, you can work things out. If not, then have a serious think about things.