My family is awful and suck the happiness out of me

I'm not talking about wife or kids, I don't have either of those. I'm a 42-year-old bachelor and I live a quiet, simple life with my dog. I'm talking about my parents and my awful sisters. My parents are in their 80s and I spend a lot of time caring for them while my sisters do almost nothing to contribute. They are both spoiled, lazy and entitled. Neither of them work and both have wealthy spouses. They're constantly antagonizing me and putting me down, while my parents express disappointment that I never got married or had children. I feel like I go out of my way to be there for everybody, and I get almost no appreciation in return. Just grief and guilt tripping, because it's never enough. It's true, I'm having a pity party but the closest people in my life don't even care how I'm feeling so I've come here to vent a little.

How do people deal with ungrateful family members who just take and cause conflict while adding nothing in return? I'm so disappointed in my siblings and even my parents, and I feel guilty for feeling that way.

Any advice?