Again, this is a personal issue and not a decision to be made by government. the first amendment already clearly states: "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof"

Marriage is a legal term that comes with benefits. Inheritance law, for example. Receiving your partner's social security payments upon their deaths, for example.

As long as their are legal benefits to marriage, it is a government issue.

Marriage is not inherently tied to religion (I got married in a park, not a church, because my husband and I were from different Christian faiths and neither of our family's ties to a church wanted to marry us without counseling to put us in the same exact Christian sect)