Again @wonderingwonderingwondering so much of what you say resonates with me. What stands out is the level of effort and resources that was put into your sister compared to you, I feel that strongly. Financially, emotionally (I use this term loosely but they were much kinder to her) my sister was given huge support and, as a result, I have a huge injustice wound, I can’t cope with any mistreatment of people, especially kids.
I came to the conclusion that they are narcissists through a lot of reading on the topic and my therapists mentioned that their behaviour sounded narcissistic (of course they couldn’t diagnose them). Like you, I did have some nice memories but I now see that just because a parent buys you something or says something nice to you doesn’t give them a pass to abuse you. So, in a way, the label doesn’t even matter, their behaviour is just abhorrent and not how any normal parent should behave. That’s the true damage they do, I think, they mess with your understanding of what constitutes abuse and your self worth and esteem is shot to pieces and then your whole life going forward is impacted by that abuse. That’s what I can’t forgive them for. The terms narcissist, personality disorder, emotionally immature have all been mentioned and all I know is that whatever label they have they’re not safe to be around.
The performative empathy is another one, in my mother’s case you can see she really isn’t sorry for the person but will make all the right noises. When I see her in action I find it chilling. Her sis in law died a couple of years back and I’m sorry to say she was in her element being in the centre of it all, sickening behaviour. 100% yes to the disgust at seeing a former close person (your sis boyfriend) being ripped asunder, especially when they would previously been treated well. My NM had an old friend and the things she would say about her would revolt you, even when the woman was dying of cancer, her version of sympathy, empathy and humanity shown towards her was messed up in private but in public a totally different face shown. My parents are working class and my NM would have a lot of shame about this but she will also look down on anyone “beneath” her, its withering.
Im so sorry that at your time of need you have had no support, that’s awful. You are worth so much more than that disgusting behaviour. You sound very aware of the situation and, with time and processing, you will feel better.