Good advice from other posters on here.
I found personally that when I was chasing after that idea of forgiveness, it just ended up getting further away from me! When I gave up on forgiving and realised I was reaching acceptance instead, that was when I realised that with acceptance came a form of quiet forgiveness after all. Acceptance headlining and grief as the supporting act iyswim? 
And that felt more true than trying to force my hurt and anger and grief into the shape of a big blanket of forgiveness. I think I needed to accept the anger and trauma I felt, rather than thinking those feelings need pushing out of the way. I sort of, embraced all of those terrible huge emotions, and kind of turned them into it being right that I had these, not that they were the signs and symptoms of how wrong my childhood was, and how 'wrong' I then was as an adult, how I'd turned out not right, not healthy or complete. When I turned it into thinking 'yes, I feel all this but it's good I feel like this, I'm reacting right, and by feeling this horror at the way they treated me as an innocent little child, I'm alot of standing up for that child. Im validating that little child's hurt and right to be a child who needs her parents to be parents...'
Kinda woo as I'm not explaining it very well, but it's like, no one stood up for that child then, but as an adult, I am standing up for her. I'm standing up for me, and so all that anger and hurt and confusion and grief, becomes me caring about that child. And it's weird to talk like that child isn't me, but I still need to work on the whole 'I'm good enough to be loved by myself' thang, so until then I'd not been able to look back and help heal any of the raw wounds I got as a child and still have so some extent today.
When I had DS I was terrified. Terrified I'd be 'Just Like Her', as that was one of the cruelest things she'd say. She'd threaten me that no matter how far I ran, how much I got away, that I'd never really succeed because in the end, I was just like her. Like she'd worm her way into my soul and sit there cold and heavy as marble, in my chest. Ugh! Shiver... so that was my secret fear, that I'd fail my child as much as she failed me.
The whole pregnancy I was terrified, I read books on attachment and baby pyschology as I planned to 'fake it til i made it', if I was really going to be like her.
Batty when you think about it really! Scary to think she had such a grip on me that I really believed in my heart that I was 'just like her'.
And the relief to find I wasn't! Oh my God I can't tell you the weight it lifted!
As soon as I saw DS, in the hospital, I knew I'd never be like her. I don't have it in me to be like her. Thank God.
And as DS grew, through the days and nights and weeks and months, I revisited my memories of some of the worst stuff that happened, with the eyes of a mother. And it released me from seeing through the eyes of my mother... for the first time I knew clearly what she did was wrong and there just wasn't any way of excusing her behaviour, and absolutely no way that I was guilty of making her behave like that. It took me looking at DS and the utter revulsion I felt about anyone ever hurting him or making him responsible.
So, that helped a lot. Decoupled me from her and from seeing things through her eyes.
I tried a couple of times to discuss it with her, but I realised that she will never admit what she did, and she will change, and she will never be accountable for her own actions.
It was then that I gave up chasing after forgiveness. I didn't know how to do forgiveness without resolution.
But I cut contact down to a bare minimum, and worked on healing myself and that's when I realised the full extent of the damage my parents had done, and that I was never going to be able to understand what had happened... child abuse isn't understandable, because a non abusive parent just can't 'get' how anyone could be so self absorbed and without empathy or even guilt. It's sort of good that you don't get it, iyswim?
Sadly, I couldn't go no contact, although I know that would have been the best thing. And new things have come to light / are still happening that mean the wounds can't stay closed and healed. Which has been really frustrating, because I've realised it's virtually impossible to heal if someone's poking your wound from time to time. But I just try and stay as low contact as possible, and try to insulate myself against interactions where she does the same stuff she always has, which shows over and over again how little she cares about me, or her only grandchild.
I did get some answers, after my dad died, from an aunt who I'd never spoken to before (isolation and divide and conquer being my mothers special skills). Her chatting and reminiscing really helped me understand that my mother was already very damaged and in the grip of an undiagnosed mental health issue before she had me. Her behaviour was so extreme and weird that I'd always thought she wasn't very healthy, but internalised her blaming me, or anyone else for her misery. But I think now, she has a serious mental health problem, I wouldn't know what exactly as it's not my place to be an armchair psychologist, but there's definitely something major going on to do with her basic personality or way she functions. And from the stories of her youth and early marriage, it sounds like she's always been that way. Which makes sense of a lot of things, but doesn't absolve her. It's the fact that she didn't ever try to get help for herself or do anything to stop herself doing damage, she just let herself run rampant over everyone, and sod the consequences, let everyone else suffer. It doesn't excuse the intense selfishness, and why her desires, paranoia and cruelty were the only things that mattered. I'm using extreme language to describe her, and aware I sound disproportionately blame-y/ ungenerous towards her. I should probably say that her selfishness (& other factors) led to the death of my sister. And my sisters suffering for years beforehand. And her combined with my dads fear and weaknesses, led to his early death too. So... although I've put it to bed as much as I can, when I think about it, it does get the emotions flooding back. Tricky on a thread about forgiveness! I think I'm further ahead on that journey about her abuse of me and my childhood. I have to deal with the other stuff somewhat separately in my head as it got revealed later, with me being an adult, and is so very huge I can't get it all in my head at once.
Anyway, back to the abusive childhood side of things...
I know I'm not perfect, but it helps to see the differences... she had dc, and didn't care that she damaged us terribly, and made our lives a living hell. And there's me worrying I might not be a good mother, and reading all the text books etc, determined to built attachment with my baby and get any help I could do I didn't fuck him up or damage him in any way. And seeking out experts to check I wasn't repeating history. I know we live in different times and I wouldn't expect her to have done anything the same, but she didn't do anything except justify her own self and take out her frustrations and unpleasantness on her child.
So, I guess I reached a sort of acceptance that what happened, happened, and that I would never get my family to recognise the reality of what they did, and that I'd never get an adequate answer.
But I could stick up for that poor emotionally ripped apart child, looking back to me, when I was so lost and alone. At least I care about that little one, and I just pour all that love and care into my own family... so I know whatever mistakes I make with parenthood, my little boy will always feel loved, and cared for, and I'll always show him that he's important, and amazing to me. And in a way, it feels like I have eased that little child in me, somewhere deep inside, still 4 yrs old and terrified.
And I guess, that's all I feel I can do. Acceptance, with a side order of forgiveness.