There are two genders and there is a good reason for it. Other than gene refreshment, males ad females have innate characteristics that children should and have the right to learn and identify with, or correctly understand biologic factors regarding reproduction. Same gender parents ARE out of the ordinary and confusing for young children, which eventually makes them feel as "freaks", cursed or other negative self-understanding.
Main reason for marriage was, is and always will be the consequences of heterosexual activity. The government has a vested interest to have mentally clear-headed members in society. Therefore government should and will be always be involved in marriage and that is as it should be.