Step-mother cheating on elderly father who wants divorce, but she controls everything. What avenues are open to us?

Since your fil has suffered several strokes and it appears you do not have first hand knowledge of what is happening, I think before anything you need to ascertain if his accusations have any basis in reality. He may be developing vascular dementia, and paranoia often goes along with that. If his wife has behaved well up until now for the 30 years they have been together, I would really question his view of things.

So #1 check out his health, which I recognize might be difficult, but I would go into the situation being supportive to both of them. You haven't heard her side yet. My mother developed vascular dementia and had paranoia and delusions about what was happening to her. She told a good story to family at a distance and they believed her. Fortunately I knew what was true and what was not true. His dr/geriatrician should do a thorough neuropsychiatric evaluation. I presume they have checked on him regularly since his strokes.

#2 - If you find that, indeed, what your fil says is true, and he decides to divorce his wife, consider carefully whether or not you can manage 24/7 care of him in your home. Do you both work? You may need some physical adaptations to your home to make it safe and manageable for him. In time he may need bathing and toileting help and so on. Are you both prepared to do this? Of course, his daughter, your wife, wants him to be comfortable in the time he has left; however, there is more than one way to achieve that. These days assisted living accommodations can provide excellent care and environment if he has the funds.

#3. Does your mil have POA financial and medical? Depending on how things work out, you may need a consultation with a lawyer who specializes in elder law.

Good luck to you. It looks like a rocky road which ever way it turns.

What proof does your father-in-law have that his wife is cheating on him? Strokes are leaks in the brain that can cause damage and to what extent thinking is affected is anyone's guess. If they have been married for 30+ years, I am leaning toward this is an hallucination of your father-in-law and my suggestion is to talk with the step-mother, tell her what he has said, and see what she says. Maybe she needs a respite and would send him for a visit, or she may react differently. Communicate, communicate, communicate. Time has a way of sorting out a lot of confusion.

It could be delusional. I had to stop going for coffee at the local Starbucks because my husband thinks that I am meeting one of the guys. I try not to leave the house between 12 and 2 because I am probably meeting a guy for lunch. My husband has dementia

My husband had vascular dementia and often thought people had broken into the house and stolen various objects that he couldn't find. He told his children that I was trying to "put him away" and take his money (actually my income had always been about double his, but they didn't know that). He wouldn't go stay with his kids when I went out of town because he thought I was plotting to sell the house out from under him, totally untrue and not possible anyway. Then when I followed his health care directives, made years before, for no feeding tube, his children accused me of murder to take his money. After his death, I divided the money in his bank account three ways for them, but they still cut me out of their lives.

Even if there is a grain of truth in this and she is seeing someone else she seems to care for your FIL and has not abandoned him, they have been together for decades and she has been his caregiver for almost a third of that time. I'm sure this is not the happy retirement either of them had planned together, she may be lonely and in need of the companionship he can no longer give.

For those of you worried about "gold diggers" did you notice that this woman has been married to the FIL for more than THIRTY YEARS? Come on, she didn't marry him 30 years ago hoping he would die soon.

FIL had strokes 8 years ago. His mental state then was such that he allowed his wife to handle all financial matters. I wouldn't automatically assume that he is in his right mind or that any fraud was involved. Adults should get to make their own decisions, including bad decisions. But when an adult is cognitively impaired those who love him should try to prevent self-destructive decisions.

I think it is imperative that this man's daughter find out what is REALLY going on before supporting his decision to get a divorce.

My husband developed dementia when we had been married "only" 30 years. He went through a paranoid period when he accused me of stealing his money, holding him captive, etc. Fortunately his daughters were not half a continent away and could readily tell what was going on. They were extremely supportive of me as I took care of their father.

Maybe the FIL in this case is not delusional. Maybe a divorce would be a good decision. But I'd sure investigate the situation thoroughly before coming to any conclusions.

My wife's father wants divorce from his wife who has POA

Married for decades doesn't always mean happily married. My parents were a perfect example of that, and I always wondered why they never split but now I know why. If dad would've left her despite her killing my sister and being a cheater and child killer, she would've been sleeping under a bridge somewhere because she couldn't get a job, no one would hire her. She lived off my dad her whole life and never worked. They were very unhappy despite being married for decades. Married for decades doesn't always mean happily married as was the case with my drunken abusive parents. There may be some things the outside world doesn't necessarily know until a child is removed from the home, which is when the real truth comes out. People tend to envy people who are married for decades and they wonder what makes them tick. Being married for decades is good if you're happily married, torture if you're not. I speak from experience from years of observation before my eventual rescue. We had to look and act perfect to the outside world as not to tip our hands to the "secret". My mom was definitely a gold digger and most likely so was my dad's lady friend after mom died, some people are just too greedy to care for their own kids, and they would rather kill them. If they survive abuse that should've killed them, the abusive parents tend to never make it right and would rather die denying their own children. I barely survived childhood and have a certain level of damage from the abuse that killed my sister. Married for decades doesn't always mean happily married, there may be some dark secrets the outside world doesn't know about.
Yes, every marriage has its problems, that's normal. However, more times than not, there are a certain number of households hiding very deep dark secrets and some couples will stay together to cover for each other in some way or another. Once again, decades of marriage doesn't always mean happily married. Something people out here are all too familiar with what (really) goes on behind closed doors in secrets as the children are coached after abuse and groomed into keeping quiet, only to be threatened to be kicked out at 18 with only the shirt on your back and nothing more. This can be devastating to any child who barely survived childhood and was always quarantined and would have no idea what life is really like outside of quarantine because they have no survival skills. Taking someone straight from quarantine and kicking them straight out into the street not caring if they survive or what happens to them speaks volumes of those who were supposed to be properly caring for that child. I'm sure someone would've caught up with me sooner or later had I stayed to 18 and had to leave with just the clothes on my back. I'm sure my abusers would've gotten in very serious trouble with the law.

I can only speak from personal experience with what I know, I can't speak what I don't know. This site request that we speak from experience and what we know, which is what I'm doing.

I've said it before and I'll say it again:

Married for decades doesn't always mean happily married, not necessarily! You never know what may really be going on until something happens that reveals what's really going on secretly behind closed doors.

Someone may be "crying wolf" here. It's best to confirm if this is an untruth.

Don't assume bringing him to Canada will get him on our health care - check it out - unless he has Canadian citizenship he will need to apply to come here & most likely will be denied as a 'drain' on the system without having made any input - check it out - recently a university prof was denied landed immigrant status because of disabled child