A specific same-sex marriage question

Okay. Lots of comments on the same-sex marriage issue, but they are not dealing with public policy issues. So for purposes of discussion, let’s try a specific example.

The compelling interest of the state and a justification for its being in the marriage business is creating stable family units. Granted, opposite-sex unions have their problems not the least of which is a high divorce rate, but nonetheless family units founded on a two-person relationship, traditionally a man and a woman, remain the foundation of a stable society.

Today, same-sex couples are part of the equation. So are children. Some same-sex unions come about after the break-up of a opposite-sex union of which children may be a part. Medical technology and adoption policies enable gay couples to form families. If, for the sake of children, society ought to stabilize families, shouldn’t government be concerned about stabilizing same-sex families to the degree it supports opposite-sex families?

Before jumping to the "yes" answer, consider this conservative concern (funny hat tip Bogus Gold) --

A same-sex headed family with children automatically creates a destabilizing force in that a third “parent” is necessarily involved. Multiple natural parents in an opposite-sex marriage are an aberration in the sense that all marriages are, initially, forever. Multiple natural parents are a requirement of a same-sex marriage.

From a public policy perspective, how should “third parents” be addressed? What are the rights and obligations of the third parent in a same-sex marriage? (That is, the natural parent of a child that is either a sperm donor or a surrogate mother for a child.) Is there an opportunity here to clarify the rights and responsibilities of that issue for both same- and opposite-sex relationships? Do third parents mean we're necessarily on the road to polygamy and polyamory?

Simply saying that to raise such a question is homophobic and bigoted is not debate. To use the existence of the problem as an “ah ha” reason to deny validity to same-sex couples probably warrants the charge.

So, my question, is their a workable solution? Discuss in comments.