My condolences, Robo. In Jan 3, 2000, my mother was diagnosed with stomach cancer. I stayed with her in the hospital some nights. It was the toughest thing I ever went through. On May25 ,2000 she passed away. It liked to have killed me. She had raised me and my sister since our Dad had died at 40 yrs old in 1955.
Then on July 4, 2001, my stepdad died suddenly. He and mother married when I was 18. That didn't bother me too much since we didn't have much of a father-son relationship.
In April 10 last year my sister died suddenly of a heart attack. She had been living in mothers home but had just moved into a nursing facility. She and I did not have a good relationship but since I was the only one left, I started taking care of her. At first I didn't want to but duty called. Now I wish I had done more, but I think that is normal. I miss her as much as my mother now. That is all my family that I grew up with.
There is no good way to deal with this. What ever you do now will not be enough down the road, that is human nature.
Just do what you can, knowing in you heart that it is all you can.
It will help them just knowing that you are there and that you love them.