I have built two startups while working fulltime and raising 2 kids. The first startup failed once my co-founder left town, after the business model and app were about 90% completed. My 2nd/current startup is http://targetmobi.com.

My schedule M-F for the last 3 years has been: 7am wakeup, feed kids etc. 9am - 5:30 work fulltime. 5:30 - 10pm family time. 10pm - 1am Startup time!. Yes thats 5-6 hours of sleep! Trying to do a startup on the side with children has been very challenging for me. Maybe its the biz models I am trying to tackle. Maybe building simple iphone/ipads apps would have had a better ROI.