You have a long difficult journey ahead, my friend. Likely one in which your acts of support and kindness will largely go thankless and unappreciated, I'm afraid. You have to realize that each one of us could be rendered helpless and completely dependent on others in the blink of an eye, by some catastrophic illness or accidental injury. What you do for you parents, especially given your circumstances, is a supreme act of love for them, and if you think about it, for yourself. I respect you immensely for transcending your painful past to become the caregiver you evidently never had.
Topher