opinion time
I beleive that no law (any law) establishes marriage. It only recognizes what was already there. In so recognizing what marriage is and the benifit to society most goverments support this institution and even bestow certain privelages to it. Historically these benifits and privelages were given in order to support families.
I also don't beleive that recongnition based on sexual preference is a civil right. If those proponets of same sex marriage actually do beleive it is then they might take an example from the real Civil Rights movement in how to change the country. Honestly I don't even think that marriage is a civil right.