Yes it is possible, but now we have the situation that jane needs to decide, as it is obvious john will not accept a triad relationship as I also have a feeling that joe will not either. So if she wants her family life, she then has to dump joe and convince john that it is over and she will not do this again, it will not be an overnight thing, it may even take a few years, but with watching the ol' P's and Q's she can have it back. HOWEVER, joe as well would not trust her if she decided to go to him, as she decieved to get there. So either way she is in a bind. But also joe and john may not want her, so she may have to start all over again.
If it was a young relationship it would be harder to get the union back together, as opposed to a long trusting relationship.
Now Don't get the feeling I encourage cheating on your mate, as I do not, I feel it is totally wrong, but to me cheating is having an affair using deception to have it. Also if your gonna have a fling with another person it had better be Ok with your mate. If it is not then it is wrong.
Seedy