My CEO has two young daughters. She sleeps about 4 hrs a night. Its the only way she can get the work done for the startup and still have time with her kids.
There is a reason why it is twice as likely that a high growth startup is launched by those over 55 than by those under 30 http://idealog.co.nz/venture/2014/11/average-startup-founders-age-creeping-so-average-age-nobel-prize-winners-why-age-and-wisdom-still-matter
It is because work life balance sucks. I'm lucky, my youngest is 25 now. Its not that I didn't have ideas for startups while they were teens and pre-teens, but the risk and work life balance pretty much precluded that. I had worked in a startup in my early 20s and I really did not have much time beyond work and weekend recreation.
You can be ultra-focused and productive. And you are also putting your marriage and your relationship with your kids at risk. That's just the reality of it. There are exceptions who can make it work. But be careful about the Lake Woebegone syndrome (where all children are above average)
There is a reason why twice as many high growth startup CEOs are at the age when kids are launched. you CAN beat the statistics, but recognize that you are working against the statistical trend