To the best of what I know about my husband, I don't really think he can do something of such. My husband can never have a second wife, not because he can't do it, but because we have built a level of trust in ourselves. The first thing every relationship should strive to build is trust. Trust is never given, it is earned. When you have a level of trust in your partner, at least to a particular extent you can predict what he can do and cannot do. Many marriages today, are facing a lot of problems just because there is no trust between the two partners.
A lot of women are filing for divorce because they are shocked at the revelation that, their husbands are having affairs with another woman outside. It should be understood that, there is no law stopping a man from having more than one wife, even some religions support that, but it will be a right thing on the path of the husband to have hinted his would-be wife about the possibility of having a second wife.