What should happen is the government should stop defining marriage of any form... It's not a difficult thought experiment to imagine the consequences of this:

What should happen is the government should stop defining marriage of any form... It's not a difficult thought experiment to imagine the consequences of this: hospitals refusing to allow visitation from people who are – but they do not accept as – members of your family. Employers refusing to extend health coverage, etc. Government will have a place here so long as there is dispute over the definition of "immediate family".