I am assuming what you're saying is your family is reliant on you because you currently don't have a job.
Well, it seems like they're kind of dependent, anyway. Your mother's role as your grandfather's primary caregiver is not an easy one, either emotionally or physically. Have a little sympathy for her - it's hard to watch our loved ones deteriorate.
And maybe lay off calling your grandfather a sentimental old fool. Even if he is one. Because one day, if you're fortunate, you'll get to be his age, and you'll be dependent on people and you might find yourself recollecting the past a lot, and in a way that's oh so boring to the younger generations. But it's your glory days and you remember them fondly. Days when you were young, carefree, and pain-free.
You're an adult. Please either find work for yourself and a damned fine excuse for not helping out, or leave and be done with it and cut your family out of your life, or suck it up and help out. Seek counseling if you feel it'll help but do try to do some growing up. Because from here, you're sounding an awful lot like a whiny teenager.