How to Deal with Sibling Anger Issues and Unblanaced Caregiving?

The past few years have been tough on my family. My brother passed away in the Summer of 07 after a long bought with lung and brain cancer. That spurred my elderly parents to move closer to me (since he was no longer able to help with incidents). As soon as my parents moved closer to me, my partner's mom ended up with a life-ending 11-month hospital stay that was gruelling... during that time my father demetia raced downhill and he died a few months after my partner's mom.

My mom is still alive and kicking! Kudos to her. She has COPD, leukemia and suffered a massive stroke about 20+ years ago.  That might sounds like a long list, but she's a tough cookie. She lives in a senior apartment building where she is largely independent with some care giving.

About 95% of the caregiving for both parents has been on my shoulders. When I have asked for more help I get the usual replies (you don't own a house, have children, are not married --- even though I am in a 10-year relationship, I am sure you've heard them all). I also get the "golden child" comments even though I have been very involved in my parent's retaining their independence (the driving talk, the dr talk) for about 5-10 years.

Anyway, I have a lot of anger at how my older sisters decided not to help. It's not just that they didn't help, but I swear they spent more time complaining about how they could not help than it would have taken to visit my parents! 

How have other folks worked through this? My mom is still very much alive, although by all rights she should not be :) Like I said, tough cookie. So I do see my sisters as I drive my mom to family functions, etc. I am always on edge that my sisters will go after me (as they have done in the past, though I am no saint here either, I have responded in ways I wish I had not). And I also worry about how one of my sisters treats my mom... I get the phone calls from my mom after my sisters berates her, either in person or on the phone... unfortunately, it is just how my sister is and it is very difficult to work around since she's a powder keg... incredibly nice or just plain mean. My other older sister tends to site in the clueless camp, ignoring requests for help or saying how if the situation were different she could help so much more.

On the bright side, my younger sister lives across country and came to help a lot during my dad's final days. She is also moving back to help with my mom. My older sisters still do the "same ol' same ol'" routine.  Right now my mom's health is fine, but I worry that everything will repeat itself should her health decline and include hospital stays... and given her laundry list of ailments, that is very probable.

I am sure other folks have run into this... how do you work through the anger so it does not consume any of your time while still facing it at family events?