I'm glad you've sorted this out in your head after talking to posters here, Starblaze. Like Hithere, I don't believe that anything anybody says about a loving mum can turn her kids against her, no matter what the genetic relationship of the other people. They might believe one or two things the other people say, but overall, IMO, you're safe.
Still, I'm glad you're writing your children a letter about NM and your brother. They need to know for their own mental and emotional safety, and, perhaps that of any children they may one day have. Like Hetty, I would just keep it simple, they don't need every gory detail, just enough so that they know there are unstable people and not to be taken too seriously. If NM/brother contact your eldest and she brings any questions/concerns to you, IMO, you should be honest but, again, brief, just answer the specific questions asked. And then change the topic if you can.... JMHO...
I've got another 'keen'... Ouch!
Well Labour’s “patriotism” didn’t last very long, did it? 🇬🇧
Last weekend, in Rutland, the first statue in Britain of the late Elizabeth II was unveiled.
What are these orange stains that have appeared on my hands overnight?