If I had my way instead of recognizing same-sex marriages I would rather the government exit completely out of the marriage business altogether and no longer ask it on tax forms, etc...
I keep seeing people say that the government should get out of the marriage business, but it seems like Religions should get out of the marriage business. Religions should be in the ceremony business, not the marriage business. Which is good because that's how things generally are. Too many people don't seem to understand that the religious ceremony is intended to make the signing of a piece of paper in front of two witnesses feel special. However, the marriage licence is provided by the state and is the same no matter what religion (if any) you subscribe to. That's not a bad thing, but too many people are making the mistake of confusing the ceremony with the actual marriage. For simplicity's sake being married in front of god conveys no legal status at all until you sign the government provided piece of paper.
The reason the government is involved and should remain so, is because there are significant and important legal implications to marriage. Beyond tax implications, there are legal issues such as inheretance (particularly important if the home is not in name of both partners), end-of-life care, hospital visitations, prison access, health benefit access, and the list goes on and on. Adn that's before we get to any provisions that are supposed to provide assitance to those raising children.
It seems strange to me that someone unmarried and living together is treated differently than someone who is married and living together or is treated differently than a brother and a sister who are living together.
Actually, people who are unmarried and living together may be treated the same as someone who is married and living together (it's called common-law), though I doubt you could claim a common law status with your brother or sister, but that's because you are assumed to not be in stable long term exclusive relationship.