It's a sad day

Neither Hawkeye nor myself have had kittens before so both of us made mistakes. She didn't know how to feed them and I didn't realize that they weren't being fed. I just figured I wasn't seeing it.
I did notice that she wasn't warming them properly even though she was laying NEAR the box and was washing them. By the time I realized they weren't getting fed, it was too late. They were only a few day sold and it breaks my heart. The first was dead when I got home,the second died an hour after I figured out he was sick. While I was sad and wished I could go back and save them, but it was beyond my reach to help them. The third was a fighter but was fading, we rushed to get her KMR and she improved... til about 8 hours later. I left the kitten on the bed while I went to look up anything I should know about hand-feeding a newborn kitten and when I got back, I found her alone in the cat bed - cold. Her mom laying on the floor nearby watching.
It was obvious she was failing and no amount of warming and rubbing and feeding was going to help.
It was so awful. I sat with her, sick to my stomach, waiting for her to recover or pass on. I know it's hard to watch any innocent baby die, but this hurt worse than I was prepared for. I found myself sobbing and realized that I was combining my feelings on several subjects. I still hurt very deeply over losing my Dandad as well as my 19 year old dog and D's new companion dog I fell in love with and had to get rid of this year and I have been dealing with infertility since last year. If I can't have the baby we planned, I could at least adore the fluffy new babies my special kitty was about to have. Instead I had to watch them die.
My darling husband buried them in the same grave as my Foxy.
This has been an emotional weekend and part of me wonders what I've done wrong. Is there a reason that this is happening, something I did wrong or didn't do at all that leaves me deserving of all the pain? Or maybe I had it too easy for too long and now life is trying to even out.
I recently decided to cut my sister out of my life. Before you judge me, I had 21 years of good reasons. My family deserved a better me than I was while she was still in my life and it was obvious that she was never ever going to change. She has since given birth, my younger sis told me the news while I was on vacation. She had a c-section and then had infections from it. I found myself totally disaffected by it. Normally I am a very maternal, very baby-excited person but knowing the kind of person SHE is and the kind of mom she has proven herself to be ...... I know I will never see that baby. I have a nephew out there in the world I will never get to know. I suppose if keeping my heart from being broken yet again, then it's completely understandable that I have no personal and deep reaction to the news. Last time I loved those boys as much as I've ever loved until I had my own children, only to watch her hurt them and then I lost them. At least this way my family gets a better me, I don't have to watch the destruction or lose a nephew again. I can only pray that the baby's dad is a loving and responsible man who will do anything to keep his son happy and healthy, no matter what my sister does.