Either his kids are older or he has someone else doing most of the parent work.
Yup: you're right. There's constantly stuff that needs to be done. My kids are between 4-11. So we're out of diapers and potty training (which is huge).
I just keep finding spaces where I can create: early mornings, late at night, or during my lunch hour.
I answered this below, but basically every weekday between 5:30pm-8:30pm is family time (dinner, chores, bedtime routine). After that, I might try to build something if I have energy. Otherwise, I try to go to sleep. Weekends: wake up early and work on projects in the morning. Rest of the day is usually family activities.
None of this is perfect. I definitely don't have a perfect routine, and I definitely have that "hard life stuff" too: http://justinjackson.ca/real-life/
Edit: I should mention that I get a lot of work done in "fits of inspiration." Meaning: if I can't sleep, and it's 1am I'll work until 4am if I'm energized.
5+ is a great time when they can actually survive by and entertain themselves; And, going to school during the day relieves pressure too.
My side project schedule is about the same except starting a little later. I also try to work on things during tiny breaks (5-20 min) e.g. the bus, a waiting room, etc; Most of this time is sketching some diagram/UI/schema. But I find it very frustrating.
My biggest downfall/problem is that I want to develop my own products and make money that way (and I am big into networking and selling), but I never focus on that. I've spent the last 3 years stuck in a never ending rut of contracting work for all of my side projects. The money is good, but it leaves me unsatisfied, and now I've been doing it long enough that I'm extremely burned out.
I have a full time job (40 hours per week), 3 kids under 10 and a side consulting job that takes from 15 to 20 hours per week where I make about an extra $80k per year on top of my full time gig.
I also take my 3 kids to their basketball games, karate, cheerleading, baseball, soccer, lego mindstorms club, etc and help them practice each of their sports at home, help them with homework, etc. In fact I recently attended a Parent University for 3 nights of 2 hour sessions to learn modeling with Singapore Math so I could help them with that homework.
What do I avoid? TV, movies, other media consumption. I think of myself as a producer, not a consumer. I also don't have any hobbies beyond the one I've loved since I was 10 years old - computers. It just so happens I can make a lot of money with my hobby.
Contrary to your assertion, it's very possible to have 3 young children and work 55-60 hours per week and do a lot of the parenting work.
20h kid time a week. Not too shabby.
Now i need this 20h a week 80k a year consulting gig of yours.
I think that's a little bit different (at least in my experience) to working on a side-project where you have your own deadlines (and can thus break them), having little guarantee of making anything for your time, and can more easily make the decision to rest one night when you're exhausted rather than keep pushing forward with the uncertainty.
I'm definitely trying to get more exercise as at this point I feel that might be the best way to approach the problem.
The 2nd thing I did to increase my motivation to actually do anything was to buy a big dry erase board and post my goals for this year. It's out in the living room, fully visible to anyone. That way I don't look like a fool for not doing anything :)
One thing I've almost stopped doing is just watching TV. Actually TV completely. I do watch documentaries from netflix and youtube on tablet while exercise-biking, washing-dishes, folding laundry etc.