The main thing you need to do is to show them what startup is about. Tell them why, how and what for startup. You must tell them the reason, how much you love your ideas and the potential in your ideas.

It is also cool to compare startup to other choices. Remember to let them understand the difference between working with passion and without it. Most people from last generation would be happy with any job. You need to understand them and let them know the world is different for you now.

I think most reasonable parents want their kids to be mature enough to make decisions. So be responsible and let your action and lifestyle speak. :-)