I have a great relationship with my parents/step parents. Out of all of us kids I'm the only one that goes and visits any of them just for the sake of visiting and I don't call on them only when I need money and I would never ask such of thing of them unless it was truly an emergency.
It's really quite simple - kids are a humongous nuisance/annoyance to me and I prefer to be as far away from them as possible. Its great that some people can be parents but that role in life has never been meant for me and that doesn't bother me in the least bit.