I firmly believe that all people should be treated equally, especially under the law. A part of that belief is that people should be treated as individuals by our government.
I don’t think that the government should get to decide what marriage means, who can marry, or how they can marry. I am also of the opinion that government should not apply tax laws, or any other legal standing, based on marriage. All legal applications, including taxes, should be defined for a person as an individual, and not to a couple or group as a unit.
Marriage is a personal choice and/or religious sacrament and should not have anything to do with legal standing. People should be allowed to configure their own lives as they so choose, how ever that works best for them. The question of legal determination when it comes to things like medical decisions, ownership of property, inheritance or even child custody should never be a question of marital status. Everyone should have the option to enter into legal agreements for partnership and to designate whom should have what legal powers in which situations, so that in the future there is no question. This would allow the individual to change those legal agreements and designations as their situations change.
That also means that there is no automatic default to a partner and everyone, be they single, monogamous, polyamorous or other, would need to consider and designate thier own preferences.