I really doubt they've got an IP lock in place; just set up a Family and invite your siblings and in-laws.
Edit: tried it with a buddy, and it is in fact IP locked; he was unable to join until I set up a VPN for him to connect through. After initial setup, you don't need the same IP address.
I believe I read that, in other for them to consider a game successful, it has to generate more profits than if they had just invested all funds spent on the project.