I think you have to pick one. Startup or kids. You can work at a burnout pace for 5 years in the hope of getting rich, or you can be there for your young children. In my opinion, if you're going to try the startup thing, there's nothing stopping you from having kids afterwards. Except that if your startup(s) didn't succeed, your skills might translate perfectly into a career that can sustain a family. And having gone that route, you might have missed out on opportunities to bond with a good partner.