At 26, I have pretty much decided that I don't want kids.
Unfortunately, what seems like 100% of my female counterparts "need" to have children, and unfortunately, I like sex and enjoy the company of women (well, most of the time). Now factor in how I would like them to have a healthy lifestyle themselves and not be a total hippy.
It's not the kids that bother me, persay, I would probably be the best father ever. I could also afford to raise a family, so that is not the issue either. What irks me is the challenge of family life (BBQ's with neighborhood parents, teenage years, attending birthday parties, post nuptial shutoff, etc.).