If you all did split and there was a dispute between you too, the government (courts) are still how things would get settled, no? Marriage I believe is just a form of contract. I believe you can write you own binding legal marriage contract that can specify whatever you would like. As a nonreligious married person, that's what I consider marriage to be. A legal framework for deciding these things. Not having one just means things won't be well defined, but the adjudication process is still similar it seems to me.