I would be fine with that. I believe we should have civil unions and religious marriages. They should be mutually exclusive of eachother. Religions can make up whatever rules they want regarding marriage. A marriage wouldn’t provide any of the benefits a civil union provides.
But since we don’t have that, we have a global term of marriage which means a lot of different things to different people. Which means we have a lot of definitions of family. Which is just fine with me. But I am agnostic.