The purpose of bigamy laws is to protect a spouse from entering a marriage based upon deceit. However, trigamy was common in the 17th C as demonstrated in the limerick:
There was an old fellow of Lyme
Who lived with three wives at one time.
When asked, 'Why the third?'
He replied, 'One�s absurd,
and bigamy, sir, is a crime.'
But these days, trigamy would be seen as two counts of bigamy. Of course, you can have polygynandry, but this is usually only seen in places like Norfolk.
I don�t think myself or Mrs O would subscribe to having a second husband and she has everything I wish for and more, of a wife.