I'm not sure exactly how young you are... but I use to be afraid of relationships (still am to a point) and I was definately scared of being married and having kids.

I'm now 31 years old and I'm actually not afraid of those things anymore... I just got out of a long relationship and I really would like to marry and have children before I'm old(er).

It really just depends on your age... if you're still a teenager then yea you probably aren't wanting to think about marrying and having children yet and that is perfectly normal.. regardless it's what you want even as you get older. Some people simply don't wish to marry or have children and there is nothing wrong with that.