The best thing I know about relationships is that communication is key. And by that I mean take time, sit down, really listen, really express, and at the end check in that both people heard each other. Yes, this is formal, but I've found it really works. My husband & I do a check in once a week. My daughter and I work together, and things can get pretty transactional--money, schedules, PR--so we always have a short personal check-in at the start of each work session.
And even in an intense care taking situation, both people should get to talk and listen. I've found that even when someone is aphasic they can still often communicate in different ways. No one can ever tell what will happen years down the line--marriages end, friendships change, children can grow away. Since all we have is the present tense of a relationship I like to focus on 1. communication and 2. enjoyment of the other person (this can be really simple--a shared cup of coffee and listening to a few favorite songs...looking at a photo album...telling a small story...etc. I've been disabled my entire adult life, was caretaker for my first husband, and now, if I'm realistic, am moving into a time when I'll need caretaking. Caretakers, I think, need appreciation, respect, and should be included in decisions. Same for those being taken care of! You ask interesting and important questions--and I hope your investigation of answers is fruitful and helpful.