The easiest option is to break up. He and his wife decided to end their marriage. Anything less deserves no less than society's full condemnation. What exactly does he need? It was after we had been married for 15 years that he admitted his attraction to men. Not to oversimplify; just merely a thought.
It's a form of cognitive dissonance.
Open in a separate window. Some even believe that being in a heterosexual relationship will restrain their homosexual impulses. There are plenty of wives who choose to stay married even after finding out later in the marriage that their husband is gay and attracted to men.
If it turns out that a husband is, in fact, gay, the fallout can be difficult to deal with, particularly for the straight partner.