Advice on my mother

Hi IM's... I need a bit of advice on how to best handle this situation & if I'm really doing the right thing as a mother? (Sorry in advance for the novel)

Rough background: I was kicked out of home before I completed school, found my feet & was able to finish my School Certificate. Met a great guy a bit older than me, we moved quick, I fell pregnant at 18 and only then did my mother turn around to reconcile. Fast forward after baby #2...

We (now) had a good relationship, which I had her new husband to thank for. He allowed her to see she could be successful & not constantly put herself down, but then it all went down hill, FAST! She had an affair, which I suspect was going on for 6-8 months. She got caught & I was the one to get the phone call from a very very drunk and inconsolable step father. He didn't want her to leave, but she did. This put a massive strain on mine & my mother's relationship.

My mother eventually went back, they argued, he took off on his motorbike & had an extremely bad (near fatal) accident. She was by his side in the hospital all day, everyday and for a month after he was discharged. Then we started to mend our relationship again.

Things were a little tense, but I didn't think things were so bad, till I got a phone call from my mother, completely distraught and struck with fear. I raced around to the rescue. They'd had another argument & she couldn't handle HIS abuse anymore. In a nutshell, there was a lot of alcohol consumed on his part and knives were brought in to it. Thankfully, when I arrived, he was completely legless!

I couldn't get through to him and told him I'd be stating the night & I'd talk to him in the morning. Then mum & I started to talk & I was furious, to say the least. The mental abuse he has been putting her through after the affair was disgusting! She was not aloud to wear a bra to work, do her hair or makeup or even have a shower, she basically had to roll out of bed and go to work as she was. Then when she came home, she had to shower, do her hair & makeup & dress "provocatively" to cook and clean for him. On more than one occasion he'd threatened her with knife fights that only one of them would get out of alive.

So in the morning, I let rip. I wasn't on anyone's side because they'd both done wrong but things seemed good for three months or so until there was another incident. I don't know to what severity nor what happened, but I decided enough was enough. I told them not to come to my house for Christmas (because I'm not exposing my children to that) & I've rarely spoken to them since, it's been almost 12 months & I don't know what's been going on with them since.

Now, should I be the adult and lay it all on the table and say "this is why you have nothing to do with your grandchildren, change it or forget it" or do I just leave it all behind? TIA xx