Any combination of people are free to make commitments to one another. It is a different matter what licenses are given out by government and what are the legal incidences of those licenses.
It would be the height of absurdity to say the people through legislation have no control over who is eligible for marriage licenses. Since it is the government giving out the licenses, the government must define how they can be obtained. We need not legislate anything about the love or sex shared by the licensees. Since there is no point in regulating combinations of individuals who do not procreate, the government properly defines the eligibility of marriage licenses to include the combination that consists of one man and one woman. That is not to say marrieds must intend to procreate in order to obtain a license. Just that they must be one man and one woman, which is the logical and traditional combination.
Again, the love and passion that one man may feel for another man is none of the government's business. Since the government is not interfering in their love or commitments, the only purpose these two men have for obtaining a license is to legalize their commitment and to obtain society's approval for their coupling. While I sympathize with their desire, it is an insufficient reason to change the legal definition.