I understand and my words are not meant as criticism. Not in the least. It is good to get these things out of our heads, to process and hopefully make room for clearer thinking.

Perhaps you might consider doing things together with them. For example, say they have a hard time eating. Invite them to make a meal together. Suggest that one of you pick a recipe and if you can, both go buy the ingredients and then preapre and share it together. It could be any mundane activity, really. Making the bed is a good one to do together, as well. Team building through day to day activities is a great way to start building motivation.

Action = Motivation.

Less talk and more doing is likely good remedy in your situation, at least to start. But starting has to happen somewhere. I would say stop putting so much emphasis on them and place more on building your relationship together. Tell them you want to go for walks every day (if possible) after dinner. Just a short, slow walk around two whole blocks. Eventually that two blocks will turn into ten and then into other adventures altogether.

Sometimes it is okay to say what you require of your relationship and going for a walk after supper (as an example) is one of those things. You want that because it helps you feel closer to them and you get to talk about your days and get fresh air together. You want the bonding.

Tell them what you want for yourself and maybe they might start thinking about what they want for themselves. This could lead to them thinking and sharing with you, how what they want may or may not match what you want. And then you both can figure out together how to provide these things for yourselves and each other.

I am rooting for you!