Nick Perry says to find out who really supports you, quit your job, commit fully to your business with no backup plan, and take radical risks like moving cities. Only then will you see who stays.
If you want to know who really believes in you, then launch that company. Quit the job everyone told you to play it safe with. Take the risk that nobody could even fathom taking. Move to a new city. Go back to the starting line. Take note of who is there so you know who to celebrate with at the finish where everyone is waiting. Quitting your job means there's no plan B. So you have to make it work. And building that company is betting everything you've got on a vision nobody else can see. Yet. And that, my friend, that's how you find out who really believes in you.