Family Ties?

There are few things in life that are as important as family, right? Parents, siblings, spouses, children, grandparents, aunts, uncles, cousins...the works.
When does it come time to cut the ties that bind?
Now, Mom lives far away, and since Dad died, her health has gotten steadily worse. My so-called aunts, my fathers sisters, haven't really talked to my mom since the funeral. My two piece of trash sisters are no help whatsoever, even though my mom is caring for my youngest sisters 3 children. She gets very little help from the state, and NO child support from any of the 3 different dads. When does it become time to tell my aunts about there lack of compassion and concern?
How about the family that I moved 2500 miles to be closer to, that I have been to see like 8 times in the last 5 years, and only 1 set of them have been to see me. Yet, several of them have driven within spitting distance of my place, and never stopped. How am I supposed to react to that? Especially since the most recent ones were on their way to visit other family members, OF MY OWN extended FAMILY!
How am I supposed to react to family that treats me like a pariah, and the fact that I can't help my own mother, and that if we had never left AZ, these things wouldn't be bothering me so much?