What can you do when baby lust gets all green eyed and ugly?

This is the new chapter in my ongoing struggle to process my miscarriage.
My baby lust has gotten envious and judgementally ugly.
The long background story is that my father was really abusive to my sister and i when we were kids. Mainly only verbally abusive to me because i was a masterfull asskisser who could figure out how to calm him down and avoid confrontation. But to my sister he was brutal and physically abusive as well because she has the same kind of aggressive temperment that he does and would always escalate the abusive situations (not that i blame her in any way because she was a child and it was my father's responsibility to control his own anger).
So now my sister is a total rage-aholic who reminds me completely of how my father was (he has actually calmed down alot now that he's older- i mean he's still a sexist prick in a lot of ways but he's not violent any more.) And she's got two children that she's really verbally abusive to. She is totally reliving the same cycle of abuse from the other side but she can't see it or acknowledge what she is doing because she thinks that as long as she doesn't hit her kids she isn't abusing them.
So now my mother has been writing me these paper letters telling me what is going on with my sister lately (I live in spain), and there is some half hopeful news in that my sister checked herself into a hospital to get help with her depression and rage issues. Which i think might be good for her if they can figure out how to help her and she can be honest enough with them so that they can.
What really hit me was that my mother said that before my sister checked herself into hospital she disappeared for a few days and her boys were with their dad (they are separated because they couldn't figure out how to stop beating each other up all the time.) And then they were with my parents (where my sister lives now, but she wasn't there). Anyway because the boys hadn't seen her for a few days my mom asked her oldest if he wanted to talk about where his mom was and when she was coming back and he told her that he didn't care where his mom was, that all she ever did was yell at him anyway and he was glad she was gone, and didn't care when she was coming back.
And that makes me want to cry because it is so sad that my nephew feels that way about his mother, and i have no idea what i can do or say to help anybody with this situation. And i think that i should be able to think of something i can do or say to him or my sister that could help. Some way to support my sister in her decision to seek help, even though she basically told me to go to hell when i told her that her behaviour worried me.
But i am so selfish twisted up in my miscarriage grief that the thought that i keep having is ¨why is the world so cruel that my f-ed up sister has two little boys- that she didn't even really want that she gets to verbally torture (and she does- i've heard it and stepped in to intervene and been totally rejected by her for that reason)-, and i- who have worked so hard to try to understand and cure my childhood scars just so that i wouldn't perpetuate the violence have a miscarriage.
And i know that the two things have nothing to do with each other. There is no cosmic baby distribution conspiracy and it's not like there is a limited number of babies and i didn't get mine because there just aren't enough.
But i have this ugly judgemental streak that pops into me way too frequently when i see some moms with their kids i think ¨why her and not me? I would do so much better.¨ And it's not just my sister it is all kinds of mothers that i sort of instinctively judge as a first jerk reaction. And it hurts so much because i feel so envious and angry and then i feel like shit because i SO do not want to be THAT SMUG CHILDLESS WOMAN who judges other mothers because they are young, or poor, or way hippy irresponsable--- or anything because society does that way too much as it is.
And i am trying all kinds of positive thinking to rechannel and refocus these thoughts when they occur but it is so irritating to be haunted by them in the first place. Does anybody have any ideas that could help?