Jane and Jon are married. Jon admitted to his wife that he's having an affair with Jezebel (not her real name :)). He says he loves both of them and simply doesn't know what to do. Jane has accepted this and is waiting for him to choose. Hopefully her. While Jane's at home needlepointing their his-and-hers hankies, Jon has taken Jezebel (okay, okay, subtlety has never been my strong suit), on a vacation, out on dates and continues to have sex with her.
Jane, Jane, JANE!
While I don't necessarily recommend a knee-jerk kick-him-out response (though there are times when that's the perfect response, as in cases of abuse or if his cheating was simply the final nail in the marital coffin), I also don't advocate giving Jon carte blanche to disrespect his family in the name of "confusion".
Jane insists she's trying to save her marriage. There are children involved, she continues to love Jon and believes he's simply in a "fog".
Jon agrees. He loves his family but can't imagine life without Jezebel.
Jon, my friends, is a classic cake-eater.
What do I suggest?
For starters, I suggest Jane give Jon a taste of life as a single guy, since that seems to be what he wants. What this means is no-one cooking his meals at home, no-one doing his laundry, offering up emotional support when he's had a rough day at the office. And certainly no sex (Jane, there are...ummm...products you can turn to to satisfy your own needs).
Jane needs to remove herself emotionally from him. Take care of herself. If this means going out with friends, let him know he's got the kids while she's out. Jane doesn't want to be passive-aggressive...just emotionally removed (not easy, but possible). For example, cook dinner for the family but let him help himself. Don't try to "sell" him on the marriage. Pursue hobbies, interests, old friends. Keep conversation civil but short. Starting to get the picture? Let him think (rightfully or wrongfully) that Jane is preparing herself for life post-Jon. The beauty of this is that, rather than push him out the door, which is what many betrayed spouses fear, it'll make Jane seem that much more attractive. Jon will start to realize that he doesn't have an infinite amount of time to "choose". That time is now. And by "choosing" Jezebel...he gets a glimpse of what he'll be giving up.
It's not a sure-thing. Jon just might decide that Jezebel is what he wants. But if that's the case, chances are he was going to reach that decision anyway. And Jane just saved herself some time and self-respect.
If he decides to stay, then it's time for Jane to insist on some rules, starting with No Contact.