I hope you haven’t been too close to this guy and aren’t living together. Has he received an annulment for his first marriage or is he still in the process of getting it?
Many couples who divorce are still friends with their ex’s. This creates a tolerable environment for children to grow up in in which they can see both parents acting civilly to one another.
However, it isn’t so great for you coming in. You would probably like his past to disappear as he starts fresh with you. But that’s not how it’s going to be. You have chosen a situation that can never be a fresh start.
If you are sure she has ovarian cancer, you have another twist in the plot, because that is the most serious women’s cancer.
Now, ask yourself if things got really bad for his ex-wife, as in she needed hospice care in five years and didn’t have money, would you be willing to take her in and help her? I have actually heard of such a thing. A friend of mine had his ex-wife come live with him for the last two months of her life. Meanwhile, he had a girlfriend living with him.
To me, the whole situation would never be worth it. I would find a man that’s free to marry, as in single in the true sense of the word or widowed. That’s it. I want to be number one all the time. That’s how I roll. But if you can handle being #2, you may have to discuss boundary issues with her, him or both. You might suggest he pays for a cab to bring her to her appointment. If what she really wants is all the support, I’d figure out if she was the one that wanted the divorce. If she was, I’d say to her, you can’t have your cake and eat it too. If she didn’t want the divorce, there may be more things wrong with your fiancé than you’ve accounted for.