For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
If you are the second, and if his first was his covenant, meaning neither were ever married to anyone else before each other, then you are in adultery. He and his first wife should be together. And you would be free to marry a never before married Christian. But if his first was married before him and she has a covenant spouse, than you are to remain married to him, and if he does leave you are to remain single or be reconciled. The only Biblical reasons for divorce is repenting of an adulterous marriage and fornication.
As was what was perceived to have beeh Joseph and Mary until the angel came and told Joseph that Mary was not unfaithful during their betrothal