What is the meaning of "Zivug Rishon" and "Zivug Sheini"? If a person divorces his spouse for reasons beyond his control, was this spouse a "Zivug Rishon"? Is it possible that this spouse was not one’s "Zivug Rishon", but rather a mistake? A person having many wives, like King Solomon and many others, who is his "Zivug"?

These terms have more than one meaning, the simple one refers to the first wife of a man and the second wife. The Talmud (Sanhedrin 22 A) states that a Zivug Sheni is not as smooth as the first, and is not the one that was announced prior to birth to be ones match for him. To what extent and in what way – that is open to interpretations of different commentators. This passage only says that it is not as simple, but not to say that one can't be happy with another wife which is not his Zivug, similarly the marriage with your "true" Zivug can come to a tragic end if they can't nurture their relationship properly. Since we can't tell today who is our Zivug I don't recommend to spend to much time on trying to tell whether your wife or divorcee is your Zivug or not. I don't know who was King Solomon's Zivug.