Not hiring parents is a great idea if you just need some warm bodies willing to kill themselves for beanies, but that doesn't say much about your company. If you're looking for people with real expertise, then you're limiting yourself greatly by focusing only on people who are still single into their 30's (not that there is anything wrong with that, it's just atypical).
Edit: the post I replied to originally said something to the effect that finding engineers without kids by age 30 would be statistically difficult. Which is false in Silicon Valley. That said, it's also not atypical in Silicon Valley to remain single well into your 30s.
I don't know where 35 years at first child came from. This is way too high for an average, even among well-educated. There might be a trend but at that age you will have all kinds of problems even with modern advances in IVF.