This is suituation that brings up significant ethical, religious and moral questions.
I should start with the statement that a living will would have most likely not prevented the current situation. Living wills only apply under certain conditions, one of them being when the person is in a persistent vegative state. This however is something her parents already dispute, so even if a living will were present they would be making a case that 15 years in a vegative state does not qualify it as "persistent". This is a dubious argument to be sure, but it is none the less their argument and one that would be sufficient to prevent honoring a living will if she had one.
As for the hubby, how long is a spouse expected to exist in what amounts to an emotional coma? It's easy for the self righteous among us to condemn him for his actions but I am not aware of any of us who ever had to have a spouse in a coma for seven years, let alone fifteen. "Judge not lest you be judged" sounds like pertinent advice here. The "in sickness and in health" and "till death do us part" clauses in most Christian marriage vows also predate modern medicine's ability to sustain someone indefinitely in this type of physical and spiritual limbo. So this is not a situation that is directly covered in the manual.
As for waiting seven years to bring it up, even if he did wait seven years to bring the issue up we need to remember that all along he was the person held accountable by her family for what would be done. I can tell you from my personal experience for about 7 days after being asked whether they should resucitate my dad one more time that there are tremendous pressures placed on you by family members who would prefer their wishes be honored rather than those of the person in question. Having been in similar shoes for even a very short time, I can forsee a situation where a spouse would continue to go along with family wishes until he reached a point where he could not longer deny what needed to be done for his well being and for hers.
Personally I don't blame him at all for falling in love with someone else and having kids because that is after all what life is primarily about. She being in a persistent vegative state does not mean he should have to live like he is in one. And while it is not politically correct to point this out, she is also not the person he married in terms of being able to give him love or emotional support so the two way reciprocation needed to keep any marriage or relationship alive and healthy is missing.
As for remaining married and the allegations that he is in it for the money. Ok. He lost his wife and endured years essentially alone due to a doctor's mistake. He's earned every penny of it and I don't begrudge him wanting to keep it. From another perspective, Teri is, or perhaps more correctly in an emotional sense, was his wife and he obviously loved her. If I were in a similar situation, and a divorce meant my mother in-law would be then get guardianship and keep my wife in a persistent vegative state for essentially forever, I would stay married as long as neccesary to prevent my wife from having to cntinue existing that way. I see it as very reasonable that he would still love Teri for what they had shared and yet be in love with someone else for the life and future they share and want the best for all involved. If someone cannot understand that, they understand neither love nor people.
On the other hand the parents' involvement strikes me as being distinctly unhealthy. It is indicitive of an extremely severe case of denial for them to expect their little girl who has been in a coma for 15 years to ever just wake up. Even if she did, she would not be "normal" in any sense of the word and there would still be serious quality of life issues. As a parent I can understand their feelings and I have empathy for them. And given that one of my son's best freinds and soccer teammate is currently in a coma with some very severe brain damage following a motorcyle accident, I and my wife have also recently considered what we would do in a similar situation. We would without question do whatever was possible if we felt our son would potentially recover - but only until that hope was no longer reasonable. Statistically, the longer a person is in a coma, the poorer the prognosis and doctors and neuologists speak in terms of days, weeks and months in that regard - not years. If a person is out more than 30 days, the prognosis of a full recovery is close to zero. She is pushing 5500 days. When is enough enough? In our case, we would have let our son go long before that point.
And if our son were married, we'd support his wife in whatever she felt he would want. If anyone wants to push the religious argument, they need to take the whole thing, not just the select parts that favor their argument. The Bible is pretty clear that a man and woman leave their parents and become one flesh, so the biblical message is pretty clear that if a decision has to be made, the spouse is the one to make it. It may be hard for her parents to accept, but it is not their place to make that decision, it's his.
Then as another matter of faith, if you are in a persistent vegative state you are not exactly living in terms of experiencing the world or engaging in relationships - the very things that make life worth living - but you are not dead either. In my estimation, that leaves you in a sort of spiritual limbo neither her on earth nor in heaven. It would be closer to Hell than anything else and it's a place I'd rather not stay if I were ever to be in her situation.