no, i am not catholic. i was raised in a church where people spoke in tongues, slapped each other on the forehead, and ran along the backs of the pews. as an adult, i have not attended any one church regularly. i have mostly just met with people of similar faith. some underground churches. all over the world.
i am more interested in figuring out what kind of actual scripture people choose to follow and whatnot. for instance, some people will knowingly enter into a marriage that the bible calls adultery, and will justify it, but cannot justify continuing in a different kind of union.
for instance, lets say i had two wives. according to scripture, im only supposed to have one wife. but, the bible is clear that divorce is bad, to be avoided. so if i were to decide to live the best righteous life i can, am i supposed to divorce one of my wives and abandon her?
i seriously doubt it.
now, the Catholic church is interesting because they don't follow the bible alone, they follow their traditions, which are believed by Catholics to be divinely inspired. which is evident in peoples responses: i was asking about scripture, they responded with Catholic traditions.
to Pentecostal Christians, there is only the bible.
From an outside perspective, I would answer your question RE: 2 wives as this: the way to live a righteous life is to not have 2 wives, and if you are Christian, you should know this. If you've gone ahead, and done this anyways, (we all sin) then I'd say divorce the second wife, and keep the first--as your vow was to her, and the second marriage would be invalid in the face of your vows. Honor your word. If you have children with the second wife, then you would have obligations to them, but to not see your former "spouse" outside of parenting roles.
If you're looking to the Bible for specific passages, I believe there are some about the "2 become one flesh"
I specifically brought up Catholicism because they are about the only Church that really cares about Annulments (CoE technically has them, but doesn't really utilize them, and so do Methodists, but again, it's not central to the Faith), and thought it was a relevant answer to your Annulment question. I think I explained as well as possible the value of having the Church review your marriage, and determine if the marriage ever actually existed, if you are of the kind that think "till death do us part" actually means what it says. As an individual, who has a stake in the divorce, it would taint your judgement, and so it is best left up to people steeped in scripture, and who can try to offer an objective view. (Btw, fun fact: the RCC actually has 2 councils review your marriage, and both must approve of the Annulment for it to be granted. If one agrees and the other says no, a third council reviews and makes the final decision)