I don't have much expertise in this area, but I do know how to find expertise. I can recommend two sources.

First, see "Living a Healthy Life with Chronic Conditions," from http://www.bullpup.com, 800-676-2855. It contains three chapters that I think would be relevant to your questions.

Second, for relationships specifically, see John Gottman. He has written several books about marriage and relationships, and he has also done many video interviews and presentations. Your public library system may have his books because they are fairly popular. If not, then maybe interlibrary loan would work. I really like public libraries because they are free.

Here is a link to one of numerous videos featuring John Gottman. Hopefully it will give you an indication of what his work is about. https://www.youtube.com/watch?v=AKTyPgwfPgg&t=62s

Although I don't have a lot of expertise in this area, I do have some experience. I have been constantly surprised by what people are, or are not, willing to do. People are so different that I think questions about caregiving need to be approached on a case-by-case basis rather than with a set of general assumptions.