I cannot just marry the person I love either...lots of restrictions for all of us...that is life.
If we change things you may not have to be unmarried, I mean polygamist will want in on all the good fortune that the SSM folks want... I mean, that would be equality and all those struggles are struggles for civil rights, and they are all the same, right? And we only arbitrarily make the age 18, why not lower it to 10, right? And what even if that adheres, say your mother divorces your father and you are 18? You could love and marry either, right? Or, if you allow polygamy and polyandry, you could marry them both. Or your sister, or your son or daughter...or your brother...where will it end, because you know all these groups that will, indeed want that, will scream bloody murder and you will have to accept it under equal protection if marrying the one, or the many, you love is the only prerequisite.
What does state licenses in other areas have to do with this? Why would that have to be for this one to be valid? The sun is the only sun we have...for it to be valid must there be another in our solar system? No.