NO!
No, not in the United States or all other Western countries. You can only be married to one person at a time. You must obtain a divorce before you remarry or your second marriage would be invalid. When you knowingly marry while still married to someone else you commit bigamy which is illegal.
Ask a lawyer....
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Yes. A person can file for divorce at any time during a marrage.
Yes, a US citizen can marry the illegal alien in any state but must file for spouses residency as soon as they are married.
No there is no need to go all the way there , you can file it in the embassy.
Follow the same procedure as if the person were a citizen rather than an illegal immigrant. File the dissolution of marriage petition in the proper court in the state where the person wishing the divorce resides.
no, you must file for divorce to be legally divorsed
He can file for divorce but I doubt any judge would grant alimony.
Yes.
* It's not illegal unless the wife catches both of you and sues for divorce. It's cheap to date a married man. If he loved you then he would leave his wife, file for divorce and marry you. By dating a married coworker you could be the one that loses your job. You should not get involved with this man and move onto single men.
You can divorce in the state you live in, if you meet the divorce residency requirements. If he or she files in one state, you will need an attorney in that state.