You seem to be suffering form the delusion that there is a state interest both in procreation relative to the legal protections of marriage, and in a child being raise by two opposite sex birth parents. Both of these assertions are patently false, and it can be proven.Irrelevant? No. We're all products of how we were raised, and it shapes our opinions, and perspective.
The state does not intervene in cases of out of wedlock birth.
The state allows divorce, even in instances where children are involved.
The state allows adoption, even by single parents, and in the vast majority of jurisdictions even by homosexuals.
What is more, you've not offered any proof that a child being raised in any other situation than by two opposite sex birth parents turns out any worse than a child being raised in a traditional marriage. Feel free to substantiate your claims. You won't be able to do so.