...Are you saying that "marriage" and "having children" are one and the same?...
Not always, for obvious reasons, including medical.
...I can assure you that their definitions are quite different. Not all married couples have children - either through choice or inability....are these couples not really married?...
Yes, they are married. If they didn't have children because of medical inability, they can be no fault in that.
If they choose not to have children, they are acting out of fear, selfishness, or some other reason of choice. Some choices might be valid, others might not.
...Some children are born out of wedlock - did their mothers not really have them?...
Yes, of course they had them.
They put themselves as well as their children at a disadvantage.
...there is nowhere in the marriage vows that states that marriage must result in the birth of a child.....
That is correct.
...procreation is not a necessity of conventional marriage, so why should those campaigning against gay marriage be concerned about the ability of those couples to procreate?
Those campaigning against gay marriage are pointing out the natural reason for the marriage commitment. Exceptions always apply to every debate.
For example, I'm all for extending economic benefits to everybody, not just homosexual couples. As far as I'm concerned, that's an issue between everybody who doesn't get them (health insurance coverage, for example) and the entity who fights it (like the health insurance companies).
That is even less of an issue with regard to homosexual marriage than procreation and child rearing.
If procreation has nothing to do with marriage, than health insurance has even less to do with it.