If the greatest benefits for child well-being are conferred only on the biological offspring of both parents; and since same-sex relationships cannot, at least at present, conceive a child that is the biological offspring of both partners, in the way that every child conceived by opposite-sex partners is such; then same-sex partners, no matter how loving and committed, can never replicate the level of benefit for child well-being that is possible for opposite-sex partners.
This defect, moreover, is an essential and permanent feature of same-sex relationships; it is part of their definition, an irreducible difference that cannot be amended or abrogated by improving the circumstances, stability, legal status or social acceptance of same-sex couples.
The primary benefit of marriage for children may not be that it tends to present them with improved parents (more stable, financially affluent, etc., although it does do this), but that it presents them with their own parents.
This is the case for 98% of children in nuclear families—which most successfully fulfill the formal civil premise of marriage, that is, lifelong and exclusive partner commitment—compared to less than half of children in any other family category, and no children in same-sex families.
Whether or not same-sex families attain the legal right, as opposite-sex couples now have, to solemnize their relationship in civil marriage, the two family forms will continue to have fundamentally different, even contrasting, effects on the biological component of child well-being, to the relative detriment of children in same-sex families.
Functionally, opposite-sex marriage is a social practice that, as much as possible, ensures to children the joint care of both biological parents, with the attendant benefits that brings; same-sex marriage ensures the opposite…
