Maybe you're unaware of the fact that gay couples can adopt nearly everywhere in the US, and that lesbians can always find a sympathetic friend and a turkey baster. Quite a few have kids from a previous straight relationship. I hope that all of them are trying to raise their kids as good citizens.
In any case, are you going to make the kids in these relationships suffer because of the circumstances of their parents? And no, you're not going to be able to take all of these kids out of those homes and put them with Ozzie-and-Harriett families, there just aren't enough of them out there waiting to adopt non-infants.
There are always situations outside the ideal. But if we are obligated to equate everything, then you are essentially saying that marriage cannot exist under the constitution. If it exists even as it does in Massachusetts, it leaves some people -- poeple with children -- out. The point of marriage (who knew a 5,000 year old institution was going to need such vigorous defense) is to encourage the ideal. The gov't has an interest because where parents fail, gov't steps in. It is perfectly logical and just for gov't to recognize and define a family according to how nature defines a family.
Your trying to add too much to the scope of my post. What I said was:
"Then again, neither can possibly produce kids, and would not be considered a married couple and family - Which is why marriage exists, and why the state has a vested interest in preserving and nurturing the next generation of good citizens."
The key word here is produce. When you adopt, yout take custody of the result of sexual contact between a male sperm and female egg. In a homosexual relationship, you must go outside the relationship to come up with both of these items.