Marriage is the union of body, mind and soul. And this happens many times in one’s life may be with one person or with many persons. You are confusing Rules of Society with Astrology. Even without a divorce you can have many marriages as per the above definition. Marriage is not indicative of the rituals associated with it nor its registration with a govt. authority. Read my article “Definitions in Astrology” on my blog navagrahastro.blogspot.in