I'll comment from witnessing how intense focus on a startup during it's earliest phases can affect a family with very young kids: Founder of a software startup

I'll comment from witnessing how intense focus on a startup during it's earliest phases can affect a family with very young kids: Founder of a software startup I used to work for was highly dedicated to his work and as the company began to see success, his family fell apart. He spent time traveling to meet with his customers and occasional travel turned into constant travel. When he wasn't traveling, he was working. Eventually his wife demanded a separation and eventually a divorce. I'd sometimes be on the road with him and can recall more than one occasion when he'd be calling home to wish his kids happy birthday. I found that to be a little sad. Now he sees his kids on weekends. Lives alone in a beautiful, but empty, house. Clearly this won't be the case for everyone but unless you are able to strike a balance you might find success comes at a very high price.